
Zbc TSknivcveit^ of Cblcago 



VEGETATION AND REPRODUCTION WITH 

SPECIAL REFERENCE TO 

THE TOMATO 



A DISSERTATION 

SUBMITTED TO THE FACULTY 

OF THE OGDEN GRADUATE SCHOOL OF SCIENCE 

IN CANDIDACY FOR THE DEGREE OF 

DOCTOR OF PHILOSOPHY 

DEPARTMENT OF BOTANY 



BY 

EZRA JACOB KRAUS and HENRY REIST KRAYBILL 



Private Edition, Distributed By 

THE UNIVERSITY OF CHICACX3 LIBRARIES 

CHICAGO, ILLINOIS 



Reprinted from 

Station Bulletin 149, Oregon Agricultural College 

January 19 18 



Tlbe Ulniversltp of Cbicaao 



\ l-.GETATION AND RKPRODUCTION WITH 

SPECIAL REFERENCE TO 

THE TOMATO 



A DISSERTATION 

SUBMITTED TO THE FACULTY 

OF THE OGDEN GRADUATE SCHOOL OF SCIENCE 

IN CANDIDACY FOR THE DEGREE OF 

DOCTOR OF PHILOSOPHY 

DEPARTMENT OF BOT/VNY 



BY 

EZRA JACOB KRAUS and HENRY REIST KRAYBILL 



Private Edition, Distributed By 

THE UNIVERSITY OF CHICAGO LIBRARIES 

CHICAGO, ILLINOIS 

Reprinted from 

Station Bulletin 149, Oregon Agricultural College 

January 19 18 






Gift 



Station Bulletin 149 



January, 1918 



Oregon Agricultural College 

Experiment Station 



Vegetation and Reproduction with 
Special Reference to the Tomato 



BY 

E. J. KRAUS and H. R. KRA^■BILL 




CORVALLIS, OREGON 



The regular bulletins of the Station are sent free to the residents of Oregon who request them 



STATION STAFF 
Board of Regents of the Oregon Agricultural College and 

Experiment Station ^^^^^^ 

Hon. J. K. Weatherford, President Corvallis 

Hon. N. R. Moore, Secretary McCoy 

Hon. C. L. Hawley, Treasurer Portland 

Hon. JEFFER.90N Myers . . . .^ t li, " bVV,.' Salem 

Hon. James Withycombe, Governor of t^e ftate. . . . v „„ .^^'^ Salem 

Hon J. A. Churchill, State Supermtendent of Public Instruction ^^^^^ 

Hon. Ben W. Olcott, Secretary of °tate. . . . . . .^^^_ ■ • ; Qregon City 

Hon. Charles E. Spence, Master of the State Grange Portland 

Hon. Clara H. Waldo La Grande 

Hon. Walter M. Pierce .Corvallis 

Hon. M. S. Woodcock . . Wellen 

Hon. H. Von Deb Hellen Portland 

Hon. G. M. Cornwall ;• v • v ■ ;' V .IVj;,^ 

Administration ...President 

W. J. Kerr, D. Sc . .Director 

A. B. Cordley, D. Sc / ' ' " Editor 

E. T. Reed, B. S., A. B Secretary to Director 

MayWorkinoer Department of Animal Husbandry . ,„ ^ , 

i^epaiiiiicxii. Chief in Animal Husbandry 

E. L. Potter, B S Assistant Professor in Animal Husbandry 

E. J. Fjelsted, B. S Assistant in Animal Husbandry 

O. M. Nelson, B. b ■' 

Department of Bacteriology ^^ .^^ .^ Bacteriology 

T. D. Beckwith, M. S ■ „ V t ^ 

Deoartment of Botany and Plant Pathology 

„ T, ., ivT c Liepartmeiiu ui j chief in Botany and Plant Pathoogy 

H. p. Barss, MS.. Rp,parch Assistant in Botany and Plant Pathology 

M. B. McKay, MS. AssocLte Prof essor in Botany and Plant Patho ogy 

W. M. Atwood, Ph D issStant Pro essSr in Botany and Plant Patho ogy 

a I owIns,Ta . ; : •.•.•: ::::::::::;;:::: ::: : IsslstaSt profeslor in Botan^ and piant pathdogy 

Deoartment of Agricultural Chemistry , r^, ■ <■ 

uepariiiieiiL wi j^ft Chief in Agricultural Chemistry 

H. V. Tartar. B. S Research Assistant in Agricultural Chemistry 

R. H. Robinson, B. S Research Assistant in Agricutura Chemistry 

H G. Miller. B.S Research Assistant in Agricultural Chemistry 

IN . Cj. rSULLIS, r>. o 

Department of Dairy Husbandry ^^.^^ .^ ^^.^^ ^^^^^^^^^^ 

P. M. Brandt, A. M Assistant Professor in Dairy Husbandry 

V. D. Chappell, M. S Assistant in Dairy Manufacturing 

P. S. Ldcas, B.S Assistant in Dairy Production 

L. W. Wing, A. M 

Department of Domestic Science .^^^^^ .^^ ^^^^^^.^ ^^.^^^^ 

Department of Drainage and Irrigation ^^.^^^^ ^^^ ^^ .^^^.^^^ 
Department of Entomology ^^.^^ .^ Entomology 

A. L. Lovett, B. S... Research Assistant in Entomology 

•W. J. Chamberlin, B. S Research Assistant in Entomology 

Leroy^C™iSds' B ' S .v. v. '.v. v. v. ■.■.■.'.■.Entomologist, Hood River, Acting Superintendent 

""" Department Of Farm Crops chief in Farm Crop 

G. R. Hyslop, B.S Expert in Vetch Investigations 

H. A. ScHOTH, M. S Assistant Professor in Farm Crops 

B. F. Sheehan, M. S 

P T T MSA Department of Horticukure^^ ^^^ ^^^^^ ^^ 

C. I. Lewis, M. S. A Pomologist 

V. R. Gardner, M. S Professor of Horticultural Research 

E. J. Kraus, Ph. D Professor of Olericulture 

A. G. Bouquet, B.S Assistant^Professorof Horticultural Products 

L. F. LiNGLE, A. B ^ Research Assistant in Horticulture 

A. F. Barss, MS Research Assistant in Horticulture, Hood River 

Cjr. \j. rSROWN, X5. o 

Department of Poultry Husbandry ^^ .^ ^^^^^^^ ^^^^^^^^^^ 

James Dryden ' 

Deoartment of Soils and Farm Management ' 

i^eparimeiii ui oi^tio chief in Soils and Farm Management 
H. D. ScuDDER, B. S Associate Professor in Soils 

C. V. RuzEK, B. s nenartment of Veterinary Medicine 

Ueparimeiii ui tci j chief in Veterinary Medicine 

B. T. SIMMS, D. V. M .^^^^^^^ - 

„ „. o a Sunt Eastern Oregon Branch Experiment Station, Union 

Robert Withycombe. B. S »upt- ^iff;,,|" Pnnntv Drv-Farm Br. Exp. Station, Moro 

D. E. Stephens, M. S ^^§*;„f n™ atilFa BraLh ExpeX^ Station, Hermiston 

R. W. Allen. MS ^"iuot Soutt^nr& Branch Exp. Station. Talent 

F. C. Reimer, M. S |"Pt- ^™ Co Branch Experiment Station, Burns 

A. E: IngbTeTon.B. s\' ■.■.•.■.■.■. V////.-V.'.V.VAct'^Supt. John Jacob Astor Br. Exp. Station, Astoria 

•On leave of absence. 



Ierne Ahern 

W. L. Powers, M. S 



TABLE OF CONTENTS 



Introduction 5 

General Discussion 6 

Relations to Practice 13 

I. Cultivation and Companion Cropping 13 

II . Nitrogenous Fertilizers 16 

III. Pruning 20 

Historical 33 

Material and Methods 36 

Experimental 36 

Materials 36 

Chemical 38 

Sampling and preservation of samples 38 

Extraction 38 

Total Nitrogen 39 

Nitrate Nitrogen 39 

Carbohydrates 39 

Free reducing substances 40 

Sucrose 40 

Polysaccharides 40 

General statement 40 

Moisture and Dry weight 41 

Microchemical 41 

Free-reducing substances 41 

Nitrates 41 

Starch 41 

Anatomical Methods 41 

Presentation of Data 42 

Chemical 42 

Experiment II 42 

Experiment V 43 

Experiment VI 49 

Experiment VII 51 

Discussion 61 

Summary 84 

Acknowledgments 87 

Literature Cited 87 

3 



FOREWORD 

This bulletin is one in the series of those issued in connection with the in- 
vestigations on the problem of pollination of the pomaceous fruits which have 
been in progress at this Station for a number of years. Most of the ideas ex- 
pressed are the direct result of such studies. After having made extended 
morphological and histological investigations, and finding in them, as yet, 
little more than a confirmation of the already well-recognized microscopic sit- 
uations, it appeared that physiological and bio-chemical investigations must 
be made to establish a true basis for determination of the factors involved, 
particularly so when the variable and conflicting evidence of a wide range of 
experiments was considered. With this general idea in mind, Mr. E. J. Kraus 
was granted a leave of absence in order to continue these investigations while 
studying in the Department of Botany at the University of Chicago. While 
he was there, it was possible for him to secure in this work the cooperation of 
Mr. H. R. Kraybill, who was at that time on leave of absence from the Depart- 
ment of Agricultural Chemistry of the Pennsylvania State College . This bulletin 
is the result of the cooperative efforts of Messrs. Kraus and Kraybill and 
has been submitted by them in fulfillment of the thesis requirements for the 
degree of Doctor of Philosophy from the University of Chicago. 

Because of the nonavailability of fruit trees, it was necessary in carrying 
out the studies, to use some other plant. After considering a wide range of 
species, the tomato was finally selected, since in its general responses in vege- 
tation and fruit setting it accords very closely to those observed in apple and 
pear trees; and moreover, with few exceptions, the plants are self fertile under a 
wide range of environmental modifications, but can be rendered barren or 
sterile. 

C. I. Lewis, 

Chief, Division of Horticulture. 



{Lycopersicum esculentum Mill.) 
By E. J. Kraus and H. R. Kraybill 



INTRODUCTION 

The question of the differentiation of sexually reproductive parts, blooming, 
fruit setting, and fruit development has been a topic for investigation and 
speculation for many years. It has been approached in many different ways. 
Much has been learned; many facts remain unexplained and without correla- 
tion; not a few facts are still to be established. More recently the influences 
of self- and cross-pollination in various plants, particularly those of com- 
mercial importance, have been taken up for serious study. The whole subject 
is so vast that these studies must naturally concern themselves with special 
phases of the problem. It has been necessary to do much simple testing 
throughout a wide fjeld and variety of plants under varying conditions. 
Morphological, anatomical, and histological investigations have been and 
still are necessary for the determination of the exact structures involved. 
Physiological studies must be extended and utilized in order to arrive at any 
final explanation of the conditions observed or the determination of their 
means of regulation. Not one of these types of study can be spared as a 
means of finally bringing the problem within the limits of practice. 

More specifically the work with plants of commercial importance has 
dealt and must still deal with the determination of so-called affinities or 
compatibilities between plants in so far as fruit setting and seed development 
are concerned. This naturally has led to an investigation of the parts and 
processes concerned in fertilization, seed and fruit development, and their 
interrelation. While many of the results have simply furnished microscopic 
details of what was already well known macroscopically, yet some facts were 
added. There is still a wide opportunity for such work. Some insight into 
the mechanism and processes of abscission has been gained; much more is 
needed. The value of physiological studies can scarcely be over emphasized, 
but these of necessity must be so detailed and thorough, considering the 
multiplicity of factors involved, that at best individual investigations can 
cover only restricted fields. 

Pending the more definite working out of details through any one or all of 
the foregoing methods, the very fertile field of established agricultural and 
horticultural practice is open for study. Whether such practices are good or 
bad from the commercial viewpoint, they furnish many suggestions that 



may be correlated and interpreted in connection with the available results of 
controlled investigations. The material reported and the viewpoints expressed 
in this paper embody some of the results of such a study undertaken in con- 
nection with the fruit-setting problem, in so far as it concerns higher plants. 
Four general conditions of the relation of nitrates, carbohydrates, and 
moisture within the plant itself, and the responses apparently correlated 
therewith, will be discussed. These are: 

(1) Though there be present an abundance of moisture and mineral 
nutrients, including nitrates, yet without an available carbohydrate supply 
vegetation is weakened and the plants are non-fruitful; 

(2) An abundance of moisture and mineral nutrients, especially nitrates, 
coupled with an available carbohydrate supply, makes for increased vegeta- 
tion, barrenness, and sterility; 

(3) A relative decrease of nitrates in proportion to the carbohydrates 
makes for an accumulation of the latter; and also for fruitfulness, fertility, 
and lessened vegetation. 

(4) A further reduction of nitrates without inhibiting a possible increase 
of carbohydrates, makes for a suppression both of vegetation and fruitfulness. 

This analysis is not intended, in any way, to convey the idea that only 
these compounds — carbohydrates, nitrates, and moisture — are concerned in 
vegetation and fruitfulness, but that the study in hand is principally con- 
cerned with them and the response resulting from an alteration of their relative 
proportions within the plant. It would be extremely difficult also to draw 
rigid lines between any particular class and the one next to it; since they 
intergrade insensibly one into another and yet, generally speaking, are 
recognizably distinct. 

GENERAL DISCUSSION 

In any discussion concerning vegetation and fruit setting, it is necessary 
to keep clearly in mind their interrelation as plant functions. One is prone 
to think of them as diametrically opposite expressions, whereas in fact no 
sharp and clear line can be drawn between them. There is perhaps a pos- 
sibility of drawing a definite line of division between the production of true 
gametes and vegetation, but there are plenty of cases on record, in which 
seeds, and particularly fruits, are regularly produced with scarcely even an 
approach at gamete differentiation. It is granted that fruits are intimately 
associated with gametic reproduction in the higher plants, but that does not 
in any sense remove them from the category of vegetative structures. The 
most that can be claimed is that they are merely specialized structures, 
occupying a position between truly vegetative organs and gametes, and that 
in discussing them they must be regarded from both points of view. 

It is really necessary that this situation be brought out clearly, since in 
some of the work dealing with the question of fertility and sterility in plants 
the conclusions are based on an inspection and record of the number of fruits 
produced rather than the number of viable seeds or preferably seedlings. 
This point is discussed in greater detail later. 



A study of the comparative morphology of fruits reveals the fact that 
widely different structures may enter into the conspicuous or edible portion. 
The parts which may be concerned are axis, bract, pedicel, torus, calyx, 
petal (rarely), stamen, and carpel. The mature fruit may consist of any 
particular one, several, or all these parts separated and distinct, or firmly 
united. One structure or group of structures may develop out of all pro- 
portion to others, resulting in the wonderful range of fruit types already well 
known. But the point is, that whatever the nature or whatever the appear- 
ance of the fruit, it is a specialized vegetative part generally concerned with 
the production of seed; this seed in itself actually may be an entirely sporo- 
phytic structure.. 

There is a wide range in the external expression of the capacity of plants 
to produce fruits and seeds. There are many varieties of plants, representing 
wide ranges of families and orders, which produce mature fruits entirely 
without seeds or in some cases functional ovules, while other varieties within 
the same genus under identical conditions fail to mature fruits unless embryo- 
containing seeds are present. To discuss this situation two classes are made. 

I. Barren forms are those which entirely fail to produce flowers or fruit- 
like structures, shed such structures at an early period, or fail to develop 
them to maturity. 

II. Fruitful forms are those which do produce and mature fruits, whether 
such fruits do or do not contain seeds. 

There are three types of this condition. (1) The first is best designated 
by the term parthenocarpy, in which there is a development of the fruit wholly 
independent of any pollination of the stigmas or fertilization of the ovules. 
As a matter of fact, in many parthenocarpic forms, development within the 
ovules does not proceed beyond the mother-cell stage. The term refers to 
the development of fruit structures other than the seeds. (2) The second 
class comprises forms in which development of the flesh proceeds only if 
pollination of the stigmas has taken place. Usually also fertilization takes 
place, but there is an abortion of the embryos at a more or less advanced 
stage. In spite of the fact that seed formation is thus eliminated, fruit de- 
velopment continues to a normal, though frequently early, maturity. (3) The 
third type of development is that following normal pollination, fertilization, 
and seed development or that occurring in apogamous forms. The terms 
sterile and fertile have at times been confused with, and used in place of, 
barren and fruitful. In this discussion these terms will be used in the limited 
sense as already suggested by Kraus (28). 

Sterile forms are those which produce no viable seeds, either because of 
failure of gametic union, abortion of the embryo, or embryos resulting from 
a gametic fusion. Fertile forms are those which produce viable embryos 
resulting from a gametic union. 

The terms fertile and fertility are extraordinarily confused in the literature. 
On the one hand they have been used to designate a condition of fruitfulness 
with little or no regard for the idea of production of new individuals, while 

8 



f?^:'" 




Fig. 2— Vegetative fruits of the d'Anjou pear, collected at Corvallis, Oregon Such fruits were 
of fairly common occiirrence at the tips of vigorously vegetative branches in the fall of lal/- j- '^^^^ 
fruits were entirely vegetative structures with well-defined growing points; many intermediate torms 
were also found. 




Fig. 3. — Fruits of the Bartlett pear. Though markedly deformed, they are truly reproductive in type. 



on the other hand they have served to convey the idea of great reproductive 
capacity frequently without regard to the manner or method of the origin of 
the offspring. Again, an organism has been considered fertile if it produced 
new individuals through seed, without reference to the exact origin of the 
embryos. In the present discussion, the term fertility is limited to the 
production of viable embryos through the union of true gametes. This 
limited view really excludes a number of seminally reproductive forms, in 
fact all cases of apogamy and vegetative apogamy and parthenogenesis, using 
the term parthenogensis to mean ttie development of an embryo from a haploid 
egg without fusion with a male nucleus. Whether this truly occurs in plants 
is still a matter for investigation, but cases of apogamy and vegetative 
apogamy are found with sufficient frequency to cast doubt on some records 
of supposed fertility and to warrant a careful investigation of this point in 
any form studied. 

It seems better, therefore, when not using terms specifically to speak of 
the reproductive capacity of plants rather than their fertility. Even this 
terminology leaves much to be desired, though there is little to be gained from 
mere multiplicity of terms. There is a very closely graded series from vege- 
tative reproductivity to true sexual (gametic) reproductivity, the only sharp 
line of separation being the differentiation of true gametes and fertilization. 
Thus plants may be multiplied by stems, leaves, or roots, not at all modified 
from the average structure; by these same organs distinctly modified, such as 
bulbs, tubers, fleshy roots and the like, or by seeds, the embryos of which 
have resulted from sporophytic budding or vegetative apogamy. It is worthy 
of note, that when stems or leaves are used as cuttings for vegetative propaga- 
tion a larger percentage of them will produce roots and continue growth 
provided they are not too soft or succulent, but allowed to harden; the con- 
ditions for hardening are in a broad way much the same as those which make 
for the differentiation of fruit-producing parts. This will be considered later. 

A discussion of fruit production is naturally tied up with the question of 
fertility and sterility. The sense in which these terms are used has been 
pointed out; from that viewpoint some records of fertility in plants have 
really been records of self-fruitfulness or at best vegetative apogamy. A recent 
paper by Stout (41) discusses at some length several reports and suggested ex- 
planations of fertility and sterility; it is therefore unnecessary to discuss that 
matter here. Stout adds many instances of self and cross-fertility, and 
intersterilityinCichoriumintybus, a condition which Gardner (9) also found to 
be the case of several varieties of the sweet cherry, {Prunus avium) in Oregon. 
Stout states that the sterility probably is due to physiological incompatibility, 
but that "to what degree such incompatibilities involve pollen-tube growth, 
irregular fusions of gametes, or embryo abortion, has not been adequately 
determined." It would be particularly interesting to know the extent of 
embryo abortion in the forms which he studied. In the apple, sterility, 
unless it be otherwise in varieties not yet investigated, is due almost wholly 
to embryo-abortion, as previously pointed out by Kraus (28) . Such degeneration 
also occurs in Oenothera (Davis[6]), in certain tobacco hybrids (Goodspeed [12]), 

11 



cherry, almond, pear, plum, and tomato. It will probably be found to occur 
in a very wide range of species. 

Now th's type of sterility is of particular significance since the degree of 
embryo abortion varies, to a very marked extent, with different varieties and 
particularly with environment, using this term in its broader sense. It is 
also a fact that many varieties of fruits, particularly those which are fleshy, 
show a marked correlation between flesh and seed development; but such a 
correlation varies greatly according to the variety of fruit, and even within 
the same variety, depending upon environment or as sometimes stated, "upon 
the vegetative vigor of the plant." There are plenty of instances, however, 
of entirely seedless fruits, which develop either parthenocarpically or as a 
condition of self-fruitfulness. Vegetative vigor itself is probably really 
nothing more nor less than a response to environment. In other words, mere 
vegetative extension and fruitfulness are not separate and distinct functions 
of the plant but each is an external expression of an internal condition. One 
is much too inclined to interpret plant functions as desirable or undesirable 
from a commercial or practical viewpoint rather than a physiological one. 
On the former basis it is desirable that fruit plants be producing fruit and at 
the same time making sufficient vegetative extension to distribute such fruit 
over a large producing surface or to provide area for the production of future 
crops, whereas from the physiological viewpoint each plant can be regarded 
as an expression of an adjustment to its surroundings, or in the process of 
adjustment, whatever its condition. Such an expression may be evident only 
as a rapid vegetative extension, the formation of reproductive parts, or a 
combination of the two in varying degrees. Now the commercial grower 
seeks the most profitable combination of the two. Each has come to interpret 
for himself what is most desirable; but few growers have any considerable 
knowledge of the means of regulation. It is well recognized that it is not 
necessarily only the greatest number of fruit buds or even of fruits that is 
most desirable, but also the quality, and with perennial forms, continued 
production. 

What, then, are the factors or conditions which make for vegetative 
extension and those which make for fruitfulness? While it is not possible as 
yet to define the exact effects or functions of specific substances, still it is 
possible to point out some very definite relationships of some of them, which 
will aid in a better understanding of the problem and certainly be of value 
from the standpoint of practice. 

One of the fallacious notions nearly as ancient as horticulture itself is 
embodied in the statement that any condition which seriously threatens the 
life of a plant, induces a realization in such an individual that it is about to 
die, and therefore it becomes markedly reproductive in order to perpetuate 
itself. This point is brought out here merely because such ideas are still 
being taught and perpetuated and actually made the basis for investigation 
and recommended practices. In any case, in deference to any possible vital- 
istic ideas, it may be said that whatever may be the conception of a plant. 

12 



its responses are readily modifiable and any preconceived determination on 
its part may be altered by environmental change. 

One frequent error in much of the experimental work relating to pro- 
ductivity in plants, has been the attempt to interpret an external response 
in the light of the specific external conditions imposed with but little or, in 
many instances, no attempt to discover or analyze the internal changes con- 
cerned. Frequently important factors have been neglected entirely. In some 
experiments the apparent limiting factor, or factors, under investigation have 
played a lesser part in determining the final result than others which were 
unobserved or given no consideiation. Now it is more than probable that 
there may be groups of external influences, any one or all of which produce 
much the same internal response, and other groups which may produce 
diametrically opposite results. In other words, external conditions may 
either augment or largely destroy the effect of each other. It might be difficult, 
then, without knowing the medium through which action has been transmitted, 
to determine any specific cause merely from the evidence of some external 
effect frequently associated with it. That this is the case is apparent in 
plenty of published accounts, though they need not be considered here. All 
this means that it is absolutely essential to have a thorough knowledge of the 
internal changes, conditions, or compounds developed in response to the 
several external conditions or factors to which plants may be subjected, then 
the correlation of these, and finally a determination of the external response 
to these internal conditions. 

In this connection it is worth while to consider the oft-repeated objection 
to the carrying on of experiments under abnormal conditions. Really after 
all the idea of just what constitutes normality frequently varies with the 
experince of the individual experimenter. The normal state is generally the 
average condition, and the conception of what constitutes the average 
condition too frequently is based on what is most valuable from an aesthetic, 
applied, or commercial standpoint. The effect of an essential element or 
factor in any set of imposed conditions can best be studied only by varying it 
from the average, greater and less, and noting the changes or responses induced. 
The growing of plants under "abnormal" conditions must remain one of the 
most valuable experimental methods. 

Coming then to a consideration of the factors concerned in fruit setting, it 
is well worth while to examine briefly a few of the reports of experiments in 
various fields that are designed to provide an insight into the problem. These 
experiments will be examined largely from the viewpoint of the relations 
existing between the nitrate-carbohydrate-moisture conditions within the 
plant and the associated vegetative or reproductive responses as detailed in 
the introductory paragraphs. 

RELATIONS TO PRACTICE 

I. Cultivation and Companion Cropping. Two of the principal effects 
claimed to be the result of tillage are the retention of moisture in the soil 
and the increase in the amount of available plant foods, including nitrogen. 

13 



It is particularly interesting to consider certain orchard practices and note 
the absurdity of attempting to follow any specific practice universally, without 
due regard to local conditions, or a knowledge of the factors operating. It is 
now realized quite generally that fruit plantings under very diverse cultural 
conditions may be equally productive. The idea that the soil must be kept 
in a state of intense cultivation each succeeding year is not valid for all con- 
ditions. There are plenty of instances in which no cultivation, and even sod 
mulch have proved to be the best commercial practices to induce and maintain 
the fruiting condition. Plantings on so-called rich moist lands often tend to 
remain vegetative, if thorough summer tillage is given and leguminous cover 
crops are grown, but become abundantly fruitful if cultivation is lessened, or 
a crop of grain, or other non-leguminous crop, is grown between the trees. 
In one region, the most successful practice to bring the trees into bearing at 
an early age may be to interplant with corn or other crops; whereas, in another, 
clean cultivation supplemented with leguminous cover crops turned into the 
soil or even the addition of animal or mineral fertilizers, may be considered 
to be the best orchard management. Thus there are many and varied recom- 
mendations, each has its supporters, and of course its application. It is 
unnecessary even to attempt to record all or a considerable portion of them. 
The point is just this, through every one of these practices some condition is 
changed and that change is either an increase or a decrease of some substance 
or substances in its relative proportion to others. It is not so much the 
absolute amounts as the proportions. If, then, it is possible to determine what 
internal relationships are required for one type of response and what for 
another, what factors operate and how they operate to modify such relation- 
ships, then the correlation of these findings will aid in establishing rational 
agricultural practices. Thus on the one hand it may be desirable to increase 
nitrates and moisture, within the plant; whereas in another it may be essential 
to decrease one or both of them. This general idea is not new, but seems 
to be lost sight of all too frequently. It is quite as essential to know what is 
present in the body of the plant itself, its extent and environment, as to know 
what nutrients are in the soil. As a simple example, light and temperature 
conditions suited to a rapid photosynthesis, on the one hand, or a slow one, on 
the other, with identical soil conditions, will result in widely different responses 
in the plant. Or, again, identical conditions influencing photosynthesis with 
different soil conditions will result in equally wide variations. All conditions 
are operating all the time. It is not easy to be sure of every environmental 
condition and interpret an external result as a response to some one particular 
external condition imposed. 

Since the moisture and nitrate relations particularly are being considered 
in this article, reference is made to the findings of several investigators. 
Pickering (3) reports on a comparison of trees growing in sod and tilled 
land. In general his results favor cultivation, though on the whole the 
moisture is greater under grass by 3%. There is no record of the condition of 
nitrates. He attributes the injurious effects to toxins from the grass rather 
than to soil nutrients. 

14 



Hedrick (17) records experiments which show an appreciable gainin moisture 
in favor of cultivated plots in comparison with those in sod. He considers 
the amount of moisture removed by the grass an active agency in decreasing 
moisture under sod. "As a consequence of the reduced water supply in the 
sod plot, there is a reduced food supply; for it is only through the medium of 
free water that plants can take in food. Analyses show that the differences 
between the actual amounts of plant food in the two plots are very small." 
Gourley (13)has determi ned both soil nitrates and moisture in his experiments 
on trees in sod as compared with those in clean culture. He found that on the 
average there was about 85% greater moisture under sod, but on the 
reverse that nitrates were appreciably higher under conditions of tillage than 
under sod. The trees receiving clean culture were superior in growth and 
fruit production. One plot (IX), which received nitrate fertilizer, averaged 
higher both in nitrates and moisture but did not show a greatly increased 
yield over another plot (V) showing less nitrates and less moisture. The 
nitrate fertilizer was applied in June. It is therefore a fair question to ask 
whether the nitrate really was available to the trees, and whether indeed there 
was sufficient moisture for its utilization by the trees. This will be considered 
further under the discussion of fertilizers and irrigation. 

In a later report (14) by the same writer, particular attention is called to a 
third treatment; namely, tillage and cover crops, under which treatment 
there is an increase in moisture and nitrates in the soil and in the annual 
average growth, though it is stated that the increase in moisture content is 
"scarcely sufficient to account for the difference in growth." The yield of the 
sod plots is less than half that of the other two. It is concluded that; (l)"under 
a good system of tillage nitrates were usually present in excess of the needs of 
the trees," and (2) "moisture was not the limiting factor in the sod plots." 
It would be of considerable interest to know if the yield in the plots high in 
nitrates could be increased by the application of additional moisture and to 
determine the effect of a nitrate application to the sod plots early in the season. 
A great array of tillage experiments with various crops and with varying 
results might be adduced; the purpose in citing those above has been to give 
an example of the studies which are being made with orchard fruits relative 
to soil treatments and the changes in relations of moisture and nitrates. 
Now, it is not argued for a moment that other nutrients and sanitary con- 
ditions are not important in relation to growth studies. The point with 
which we are concerned is the fact that certain vegetative and reproductive 
responses are closely associated with a variation in the nitrate and moisture 
relations. Thus the means of regulation of these two factors and a knowledge 
of their function within the plant, are of prime importance. On the one hand 
it may be commercially advantageous to increase one or both of them in order 
to render the ultimate crop more abundant or profitable, while on the other 
hand, it may be desirable to decrease them for the same purpose. Much 
depends on the type of response desired, it might be vegetative or it might 
be reproductive, depending on the crop grown and upon its state of develop- 
ment. Furthermore, an intercrop or cover crop might be of such a nature 

15 



that through shading and reducing the light intensity, the photosynthetii- 
activities of any specific crop might be profoundly changed, a condition 
certainly as fundamentally important in interpreting plant response as soil 
environment. The kind of tillage, intercrop or cover crop adopted, therefore, 
will be determined by its influence on any one or all these factors at least. 

Gourley gives some analyses of the plants in bis experiments, more especially 
the carbohydrates. "In alternate-bearing trees we find a heavier deposition 
of reserve food material in the storage tissues when the tree has formed fruit 
buds. As starch, this is mainly found in the medullary rays and pith." No 
determinations of the nitrates within the plant tissues are given but, "It 
appears in this soil that nitrate formation of from 20 to 40 parts per million of 
dry soil as an average for the growing season is essential for the maximum 
vigor of the trees and abundant fruit-bud formation, and that above this an 
excess will not of itself increase the growth or number of fruit buds formed." 
It would be interesting to know what would be the result of increasing nitrates 
and moisture simultaneously, or of an application of nitrates very early in 
the season. 

In this connection, it is a common experience to find very great increases 
in yield or in the number of fruit buds formed during the first one or two 
seasons of tillage following the sod-mulch system, provided of course that the 
tree roots have not been severely injured. This may be due to tne fact that 
excess carbohydrates are frequently stored in plants suffering from lack of 
nitrates, the plants being in the fourth condition previously enumerated; 
namely, feebly vegetative and low in fruit production. When nitrates and 
moisture were rendered available and taken into the plant, the stored carbo- 
hydrates would be drawn upon and utilized in vegetative extension and the 
production of fruiting parts. This is the third condition described. Theoreti- 
cally by further additions of nitrate and moisture the second condition could 
be attained, and practice has often shown this to be the case. By artificially 
restricting the available carbohydrates or preventing their formation, the 
first condition can be induced. While this condition is not generally likely 
to be met with in practice, yet one means of producing it is through heavy 
pruning. This situation is discussed at length in connection with pruning 
practices. 

II. Nitrogenous Fertilizers. It is not the purpose of this paper to enter 
into the discussion of the use of fertilizers. A vast amount of experimentation 
has been done, much is still required. One cannot cjuestion that each and 
every one of the essential elements is a limiting factor in crop production; 
they are that by definition. The main criticism to be offered on much of the 
work, however, is that it has concerned only external results, sometimes with 
but little indication of how they were produced. It is absolutely essential that 
future work shall take into account internal changes and the relations of these 
to observed results. Much more information is needed on the role of any 
essential element in its varied relations to processes of water absorption, 
respiration, carbohydrate formation, translocation and storage, protein 
synthesis, and any number of other plant functions. Such determinations will 

16 



come closer really to answering fundamental questions than a record of pounds 
of fertilizer applied and yield in bushels per tree or per acre, no matter of how 
great practical or local significance such records may be. 

Here it is our purpose merely to note a few experiments which are of interest 
from the viewpoint of a nitrate-carbohydrate relationship as previously 
proposed. Russel (39) concisely sums up the general effects of nitrogen as 
follows: 

"The normal nitrogenous food of plants is, however, a nitrate, and there 
is a close connection between the amount supplied and the amount of plant 
growth, which is well shown in Hellriegel and Wilfarth's experiments. 

"The increasing effects produced up to a certain point by successive 
increments of nitrogen may be due to the circumstance that the additional 
nitrate not only increases the concentration of nitrogenous food in the soil, 
but also increases the amount of root; i. e., of absorbing surface, and of leaf; 
i. e., assimilating surface. The process thus resembles autocatalysis, where 
one of the products of the reaction acts as a catalyser and hastens the reaction. 
The increase does not go on indefinitely because some limiting factor steps in. 

"The effect of nitrogen supply on the grain is very marked. (In the ex- 
periments cited), it is seen that the grain formed, when nitrogenous food is 
wholly withheld, is only two-thirds of the normal weight per inclividual. The 
first addition of nitrate causes a marked rise in the weight per grain and the 
proportion of grain to total produce, but successive additions show no further 
rise. Indeed other experiments prove that excess of nitrogenous food causes 
the proportion of grain to fall off somewhat. The leaf and the general charac- 
ter of growth are affected to a much greater extent. Nitrogen starvation 
causes yellowing of the leaf, especially in cold spring weather, absence of 
growth, and a poor starved appearance generally; abundance of nitrogen, on 
the other hand, leads to a bright green color, to a copious growth of soft, 
sappy tissue, liable to insect and fungoid pests (apparently because of the 
thinning of the walls and some change in composition of the sap) and to re- 
tarded ripening; the effects resemble those produced by abundant water 
supply. A series of plants receiving varying amounts of nitrate are thus at 
somewhat different stages of their development at any given time, even though 
they were all sown on the same day those supplied with large quantities of 
nitrate being less advanced than the rest. If they could all be kept under 
constant conditions till they had ripened, this difference might finally dis- 
appear; but in crop production it is not possible much to delay the harvest 
owing to the fear of damage by autumn frosts, so that the retardation is of 
great practical importance. Seed crops like barley that are cut dead ripe are 
not supplied with much nitrate, but oats, which are cut before being ciuite 
ripe, can receive larger quantities. All cereal crops, however, produce too 
much straw if the nitrate supply is excessive, and the straw does not commonly 
stand up well, but is beaten down or "lodged" by wind and rain. Swede and 
potato crops also produce more leaf, but not proportionately more root or 
tuber, as the nitrogen supply increases; no doubt the increased root would 
follow, but the whole process is sooner or later stopped by the advancing 
season — the increased root does in fact follow in the case of the late-growing 
mangold. Tomatoes, again, produce too much leaf and too little fruit if they 
receive excess of nitrate. On the other hand, crops grown solely for the sake 
of their leaves are wholly improved by increased nitrate supply. 

"... The actual increase of growth brought about by successive incre- 
ments of nitrogenous food depentls on the amount of water and other nutrients, 
on the temperature, and so on; any of these may act as limiting factors." 

Hartwell (15), in reporting on starch congestion accompanying certain factors 
which retard plant growth, states that many different factors, correlated in 

17 



each case with retarded growth, were found to be associated with an accumula- 
tion of starch in the above-ground portion of plants. The omission from 
the manures of nitrogen, as well as of phosphorous, was associated with a 
marked depression in the growth of vines, and it may be seen that in general 
this was accompanied by a greater accumulation of starch than where the 
complete manure was used. A deficiency of available potassium in the soil 
was usually accompanied by an accumulation of starch in the potato vines." 
In general, an increase in the amount of the available nitrogen caused an 
increase in growth but a decrease in the average amount of starch in the vines. 
In one experiment, comparing the various amounts of nitrogen applied with 
the starch stored, the results were not uniform throughout the growing season, 
starch storage being greater in late July and very appreciably less, especially 
in the heavily nitrogen-fertilized plots, in August and September. No ex- 
planation is given; but a statement of the condition of growth at this time 
would have been very desirable. 

It seems as unnecessary to account for the accumulation of starch as a 
pathological condition, as it does to assume that its absence could be con- 
sidered such a condition in highly vegetative plants. Though the author 
suggests it as an improbability, yet it is as legitimate to assume that the 
lack of utilization of starch, or the substances from which it is synthesized, is 
just as much the cause of retarded growth as that the retarded growth causes 
the starch accumulation, though why this should be referred to as a patho- 
logical condition is not entirely clear. Retarded growth and starch ac- 
cumulation would be the expected results if the carbohydrates were not 
utilized in vegetative extension or the production of reproductive portions. 

The nitrate fertilizer experiments of Lewis and Allen (29) are of especial 
interest when considered from the viewpoint previously expressed. Their work 
consisted in applying to apple trees in declining vigor nitrate of soda, either 
as a spray on the trees themselves or as crystals or a spray on the ground. 
There was little difference in result in relation to the method of application, 
but a very decided difference depending upon the time of application. To 
quote : 

"Orchards in a somewhat run-down, or devitalized condition; namely, 
those which are making very little vegetative growth, either in twig or leaf, 
those which have thin, yellow leaves and weak fruit buds — are greatly 
benefited by the use of nitrogen. In such cases this fertilization produces 
a vigorous wood growth, causes the leaves to become thicker and greener, 
produces more and larger fruit, and thus restores the trees to normal vitality. 
There is an indication that some of the so-called pollination troubles have 
been due to the fact that while the fruit buds and spurs might have sufficient 
energy to blossom, they did not reserve food enough to mature fruit. One of 
the most striking results obtained from the use of nitrogen has been in the 
increased percentage of set. 

"It has been startling to notice the rapidity with which nitrogen in an 
available form gives results. Nitrogen added in March causes a larger per- 
centage of set of fruit in April, an immediate change in the character of the 
foliage, and a stimulation of the wood growth. 

"With about six pounds of nitrate of soda applied to the ground around 
each mature fruit tree, one secures about a pound of actual nitrogen. Such 

18 



an amount is sufficient to restore the trees to their natural vigor. Indications 
are that in many cases this amount of nitrogen added two years in succession, 
causes an over stimulation, shown by too heavy a foliage development, too 
strong wood growth, and a production of too many over-large specimens 
of fruit. 

"The experiments in 1915 indicate clearly that the fertilizer should be 
applied during the early part of March — that if we wait until May, which 
has been the custom in applying nitrates, we recieve very little benefit from 
such fertilization the year the nitrates are applied. This is due to the fact 
that the seasons are too dry to cause the proper dissolving of these fertilizers 
in time to be of assistance. The fact that the nitrogen has such a marked 
effect on the percentage of set means, moreover, that it should be applied 
before the trees bloom. 

"Our experiments in 1915 indicate clearly that the best method of applying 
nitrate of soda to orchards is to spread the dry crystals broadcast on the 
ground under the trees, harrowing soon after applying. In 1914 the indications 
were that it paid to spray the nitrate on the trees, but investigations this year 
showed that the real reason why we secured better results from spraying in 
former years was due to the fact that nitrogen sprayed on the trees was dis- 
solved and reached the roots, whereas the nitrates spread on the ground were 
added in May instead of March, and were therefore of little value. We believe 
that this year's experiments indicate very strongly that the nitrogen will be 
of value to the trees only when it reaches the roots. Further experiments 
will be conducted, however, to confirm these conclusions." 

Further experiments as reported by Lewis and Brown (30) have tended 
to confirm these conclusions. While no chemical analysis of the plant 
tissues has been made either before or since the nitrate applications, yet 
the general observed responses are so precisely similar to those in the tomato 
experiments, to be detailed later in this article, that some suggestions may 
not be out of place. It is more than likely that the trees described as lacking 
in vegetative vigor and possessing small yellowish leaves and weak, slender 
fruit buds were very low in nitrates and high in carbohydrates, especially 
starch. Brief examinations of the twigs and branches of trees of similar 
appearance and from the same locality show this to be the case. This being 
true, the trees would be in a state of low vegetation due to a lack of 
nitrates sufficient to permit the utilization of the carbohydrates in any ex- 
tensive formation or development of vegetative or reproductive parts. This 
accumulation of carbohydrates, however, when nitrates are added to the soil 
and sufficient moisture is available to permit their being taken into the trees, 
is drawn upon and is made over into other compounds and structures. Depend- 
ing, then, upon the amount of nitrates and moisture available in relation to 
the stored carbohydrates and those subsequently synthesized, the type of 
growth response would vary. Very large amounts of available nitrate, 
moisture, and carbohydrates would thus result in vigorous vegetative exten- 
sion; proportionately smaller amounts of moisture and nitrates, in varying 
degrees of vegetative extension and reproduction; and very small amounts, in 
feeble vegetation and feeble fruit production. On the other hand, if the 
carbohydrate supply was very limited, even though nitrates and moisture 
were abundant, then the growth might be expected to be weakly vegetative 
and scarcely or not at all reproductive or fruitful. 

19 



In the experiment just previously cited and in many others dealing with 
nitrate fertilization, the above range of final results in growth and yields has 
actually been recorded. Unfortunately, in the majority of these experiments, 
no analyses of the plant tissues themselves are available; so that it is not 
possible directly to analyze the results according to the foregoing suggestions. 
It may be hoped, however, that in some of the future experiments analyses 
may be made in order to test these suggested relationships. 

III. Pruning. A consideration of the factors involved in pruning in 
relation to fruit setting is particularly interesting, since by pruning, the 
organism itself is profoundly altered in its relation to its general environment, 
which usually is not greatly modified. It may be supposed that a plant at 
any particular time represents the result of all the environmental forces 
acting upon it, and it is either in a state of equilibrium with such forces or in 
a state of becoming so adjusted. The response following pruning is largely 
a process of regeneration. The type of such regeneration, whether of simple 
vegetative parts or parts closely associated with reproduction, is of the 
greatest practical significance, and any knowledge leading to a possible control 
of such responses is highly desirable. Top pruning is a most direct and 
speedy method of influencing the carbohydrate conditions in a plant. 

Pruning practices are almost as many and as varied as the number of 
individuals who grow plants. While there are almost endless varieties of 
types and combinations of types, yet through all run two fundamental ideas, 
the one to direct, maintain, decrease, or increase the vegetative extension of 
the plant, the other to maintain or increase flowering or fruitfulness. Fre- 
quently vegetation and fruitfulness are regarded as opposing plant functions. 
While at first thought this seems to be the case, it can hardly be the true 
situation; rather, vegetative extension and fruitfulness are intimately as- 
sociated one with another. Reproduction may be vegetative or gametic. 
Beginning with clearly vegetative parts used for reproductive purposes, a 
closely graded series may be constructed, through slightly modified parts 
such as off-shoots, bulbs, and the like, sporophytic budding, apogamy to 
parthenogenesis (if in the limited use of the term this really occurs in plants) 
and true gametic reproduction. The main point to be borne in mind is that 
there are not two entirely antagonistic functions, but rather extremes of 
possible expression, and that between these extremes, all sorts of gradations 
may exist. To say that a plant becomes markedly reproductive because its 
life is threatened is indeed begging the question. 

Pruning practices concern both roots and tops of plants. Much more work 
has been done and many more results recorded regarding the latter than the 
former, probably because of the ease of handling and observation. The 
comparatively limited experiments on root pruning, for the most part have 
been recorded and interpreted on the basis of the responses of the tops. 
Lacking an abundance of specific chemical analyses of the plant tissues in 
connection with pruning experiments, much of the following discussion must 
be based on inference. The conditions imposed and responses recorded, 
however, agree so closely with similar circumstances and results in the 

20 



experimental work detailed later in this article that the specific, suggested 
explanations seem worth presenting. 

One of the most general statements regarding pruning of fruit trees is that 
heavy dormant pruning increases vegetation, that trees should be pruned to 
cause them to grow more vigorously. The inaccuracy of this general state- 
ment has been pointed out, particularly in three reports. The Duke of 
Bedford and Pickering, found in comparing trees 12 years of age that heavily 
pruned trees were 16 percent lighter than moderatly pruned trees, while those 
unpruned were 20 percent heavier than those moderately pruned. Alderman 
and Auchter (1) found that young trees lightly winter pruned as compared 
with those heavily pruned were taller and broader, made longer total growth, 
grew branches which were longer and larger, had larger trunks, and exhibited 
a tendency toward earlier bearing as indicated by flower-bud formation. 
Gardner (11) in experiments in winter, winter-and-summer, and no pruning on 
young trees found that on the average the unpruned tree increases in size as 
rapidly as, if not a little more rapidly than, the tree that is winter pruned 
only or both winter and summer pruned. 

In the case of the older trees, "not in a very vigorous condition," Alderman 
and Aucher report, as a result of heavy and light pruning, an exact reversal 
of fruiting habits from those in the younger trees. "Both the Arkansas and 
the York Imperial varieties produced distinctly larger crops on the heavily 
pruned blocks than on the lightly pruned blocks. This sharp distinction in 
bearing habits between vigorous young trees and middle-aged trees of subnormal 
vigor is of interest. Middle-aged is only a relative term. In New York 
where apples are still in their prime at thirty-five years of age, fifteen-year old 
trees would be considered young. In the Shenandoah Valley the commercial 
orchards generally start their decline at twenty-five to thirty years of age 
and fifteen to twenty years is truly middle age. We know that neglected 
orchards which have not produced crops of any consequence for years will 
frequently be greatly benefited and stimulated into fruit production by a 
heavy pruning. To be sure such trees are abnormal, but it will be noticed that 
the trees in this orchard made but four inches of terminal growth in the year 
before the experiment began, and that since that time they have averaged 
from seven to nine inches for one variety and from four to five for the other. 
This result would indicate that at the beginning the trees were somewhat 
below normal in vigor, but under better cultural methods their average 
condition had improved. The writers are of the opinion that, from the stand- 
point of fruit production, vigorously growing trees would have made a 
somewhat different response to the treatment than did the ones in the test." 

Both Kraus (27) and Gardner (10) have pointed out that the thinning out of old 
massive spurs in pears, apples and prunes, results in a much greater tendency 
of the fruit buds to mature fruit. In brief, to prune "judiciously" in order 
to maintain the desired balance between fruiting and vegetation, is a very 
general recommendation, but how many of those who make the recommenda- 
tion understand what factors are involved in producing the results? 

Now, why these apparently diverse results from similar practices? An 

21 



analysis of some of the internal conditions affected and their relation to external 
response may aid in obtaining a clearer view of the situation. In the first 
place whatever may be the character of the storage in the top under any 
condition, it is self evident that some will be removed from any future use 
by the tree if any pruning whatsoever is practiced. Considering now the 
responses during the growing season on the basis of the suggested idea of a 
moisture, carbohydrate, nitrate relationship, it may be assumed that at the 
actual time of pruning the soil moisture and nutrients themselves would 
neither be increased nor decreased whatever the practice, though the amount 
utilized later by the tree would be profoundly modified. On the contrary, 
any pruning practice would certainly mean a decrease in the amount of storage 
materials actually remaining as a part of the plant, and in large measure also 
the future synthesis of such material, so that the relation of the nutrients in 
the plant to those in the soil about it have been profoundly disturbed. That 
is to say, top pruning, whatever its nature, would decrease particularly the 
available carbohydrates and other stored substances in relation to the soil 
moisture and nutrients; root pruning would not only do the same thing but in 
addition would tend to prevent, in considerable degree, the possibility of 
absorption of materials from the soil. As will be pointed out later also, in 
the more detailed experiments on tomatoes, the amounts of moisture and 
nitrates which are absorbed and used in growth are dependent upon the 
available carbohydrates either in storage or those being derived from 
photosynthetic activity. 

Thus, as previously pointed out, the four general types of response related 
to the varying nutrient conditions, could be expected from pruning practices 
as well as any other practice which would tend to modify them. If, for 
example, either because of lack of storage or photosynthetic activity, the 
carbohydrate supply were greatly reduced, even though there were an abun- 
dance of available moisture and nitrates, then blooming and fruit production 
are very greatly decreased, and vegetation is also restricted. The suppression 
of vegetation in itself is absolutely no reason why fruitfulness should follow.* 

Again, if moisture, nitrates, and carbohydrates all are abundant, these 
would be utilized in rapid vegetative extension, with little tendency toward 
the formation of specialized reproductive parts or the storing up of large 
quantities of carbohydrates, as long as growth was active. This condition 
differs from the preceding in the availability of the carbohydrates. If, then, 
a pruning of any type were given to trees or plants with meager carbohydrate 
reserves or means for their continued synthesis, even though the nitrogen and 
moisture conditions are unchanged, there would be a tendency for decreased 
vegetation and fruiting. That this is the actual situation is evidenced by the 
recorded results of many investigations, especially those dealing with young 
or so-called vigorously growing plants. 

A third condition exists when there are available nitrates, moisture, and 
carbohydrates, but the latter are synthesized in excess of the quantities which 

*(The effects of etiolation naturally suggest themselves, but these seemingly must be rather 
sharply separated from the discussion at hand.) 

22 



are utilizable in simple vegetative extension. In such cases growth is expressed 
both as vegetative extension and specialized reproductive parts, either as a 
sort of balance or as an expression in favor of the one type or the other. Com- 
pared with the preceding condition, actual vegetative extension is apparently 
less. It is this condition which is of greatest commercial interest to fruit 
growers. It is an ideal condition to have trees making some vegetation each 
year, thus increasing and maintaining bearing area coupled with abundant 
fruit production. This nicety of balance can be and is maintained through 
many orchard practices, expecially such soil treatments as will regulate nitro- 
gen and moisture conditions, and such top treatments as can be managed 
through pruning. Sometimes no cutting whatsoever may be needed, but 
generally some is required. The desired results of such cutting might be to 
suppress all growth in one portion, encourage growth in another, or to maintain 
a balance between purely vegetative parts and reproductively modified parts 
in still others. These conditions could be regulated by severe or light cutting 
depending upon the relative abundance of the carbohydrates, nitrates, and 
moisture, pruning furnishing the most ready practical means of regulating the 
form. 

A fourth condition is most frequently encountered in very old trees, in 
those which are growing in impoverished or dry soils, or in those which have 
sustained certain types of injury which virtually amount to a ringing or 
girdling. In these cases vegetative extension is notably depressed, the foliage 
small and generally light colored, and there is usually an increased tendency 
toward flowering, accompanied or not, as the case may be, with fruit develop- 
ment. In many instances there is actually a relative decrease in the pro- 
duction of flowers. If this condition is due to a relative lack of nitrates or 
moisture or both in proportion to the available carbohydrates, then it might 
be expected that if the former were increased, there would be first a tendency 
toward increased vegetation and fruiting, but on increasing these amounts 
more and more, a response wholly vegetative would finally result. Such 
increase could be brought about either by some top pruning which directly 
removes stored carbohydrates, or by increasing the available nitrates and 
moisture by the application of nitrogenous fertilizers and cover crops with 
or without irrigation, as the case may be. Both these methods and their 
gross results are well known and established in practice. In general, it may 
be added that for most tree fruits, a combination of the two is most useful, 
since if the available nitrogen is very low, to secure results by pruning alone, 
the potential bearing area must be so greatly reduced that the trees are no 
longer commercially profitable. On the other hand, the application of 
fertilizers or cover crops only without some pruning may result in a loss of 
some of the most profitable bearing area by over-crowding or the development 
of fruit of a poor commercial grade. 

With this viewpoint and suggestions as a starting point, it is of interest to 
consider the recorded results of several investigations. 

There is a wide range of opinion among horticulturists in general regarding 
the response due to summer pruning; that is, pruning when the plants are in 

23 



actual foliage. Formerly it was stated that summer pruning induced fruitful- 
ness. This view is changing, due to the accumulation of results of accurate 
experimentation. One might expect much the same results from summer 
pruning as from winter pruning, and such is not far from the true situation. 
There is absolutely no question but that growth or vegetation may be de- 
cidedly decreased by cutting in full leaf but it must be remembered also that 
fruitfulness is not a necessary accompaniment of reduction of vegetation. 
It may be quite as much associated with an increase as with a decrease, as 
previously pointed out. 

Summer pruning differs in one marked essential from dormant pruning, 
especially when the plant in question is leafless in its dormant stage, in that 
the former removes not only whatever nutrients are in the portion cut away, 
but also removes an appreciable portion of the carbohydrate synthesizing area. 
It must be remembered, however, that while some leaves are removed entirely, 
yet in some portions of the tree, other leaves may be exposed to the light to 
a greater extent. In other words the decrease in synthesizing power may or 
may not be entirely equal to the leaf area removed. Again, moisture and 
nitrates are apt to be present in smaller quantities during the mid-summer 
growing season than in spring, so that they, as well as a restriction of carbo- 
hydrates, would act as limiting factors to growth. With these facts in mind, 
whatever else has been said of dormant pruning in the ratios of nitrates and 
moisture to carbohydrates in relation to growth, apphes equally forcibly in 
summer pruning. 

The term summer pruning has been used to include a wide variety of 
pruning practices followed out during the summer months, such as a thinning 
out and heading back relatively early or late in any given season or at several 
times during the season, removing water sprouts or large limbs, or merely 
pinching the tips of branches. At times it has been employed in connection 
with winter pruning. Much of the disagreement between the interpretations 
of investigations is because of different methods employed. Actually, so far 
as can be deduced from the data available, the results are remarkably well 
agreed. 

Batchelor and Goodspeed(2) have reported on summer-pruning practices. 
The data recorded permit only a suggested interpretation of the results. 
There are many possible combinations of causes operating. The greater 
average length of 100 twigs in each case, does not indicate whether the winter 
and summer pruned trees actually accumulated more total volume of growth 
than the unpruned trees. The mere weight of the fruit produced also leaves 
doubt as to the general fruit-bud situation, the percentages of blossoms setting 
fruit, where the functioning spurs occur, and other points. It is quite probable 
that as the authors suggest, the decreased fruit production is due to a reduced 
area of fruit-bearing wood removed by the summer pruning. ' At least, if fruit 
buds were stimulated as a result of the thinning (pruning), they were not 
sufficient in number or quality to compensate for those removed. It is not 
possible to judge these results as they stand on the nitrogen, moisture, carbo- 
hydrate relations, for lack of sufficient data. 

24 



Alderman and Auchtcr (1) report on summer-pruning experiments, which in 
net result of fruit production approximate those just previously discussed. 
The experiments included heavy, moderate, and light pruning in the form of 
a heading back and thinning out. The light pruning evidently was almost 
entirely in the nature of thinning. A proper relation, however, was always 
maintained between the heavy, moderate, and light pruning. In one orchard 
the degrees of difference in pruning were secured entirely by varying the 
amount of branch thinning. 

"In all orchards dormant pruning took place between March 20 and April 
4 of each year. The summer pruning practiced was of virtually the same type 
as the dormant pruning and in amount of wood removed corresponded closely 
with the moderate dormant pruning. The early summer pruning was per- 
formed in 1912 between May 25 and May 31, but in the last two years was 
shifted to June 9 to 11, as the earlier pruning seemed to be much too early. 
The midsummer pruning took place each year between July 8 and 15, while 
the repeated summer pruning was simply a combination of the early and 
midsummer prunings and took place on the dates mentioned. In this region 
fruit-bud formation in the apple begins from June 20 to July 1. Early summer 
pruning was performed just previous to this period and midsummer pruning 
just following it after the period of most rapid growth was completed . . .In 
the case of the winter and summer pruning, the trees were headed back in 
the winter and about one-half of the wood was thinned out. In the summer 
time, the other half of the wood was thinned out and the suckers were removed. 
In the case of the repeated summer pruning it was attempted to do the same 
amount of pruning at each date. The sum of these two prunings made about 
the same as the moderate dormant pruning and left the trees pruned in about 
the same condition as regards shape, etc." 

The results of the experiment to test the effects of seasonal pruning upon 
the first five years' growth of trees "show that the trees pruned heavily in the 
dormant season made by far the longest average terminal growth. The sum- 
mer-pruned trees made a longer growth than the trees pruned lightly in the 
dormant season, but did not make quite as much growth as did the moderately 
pruned trees." But the authors made a measurement of the total as well as 
"average" growth produced in the year 1915 and the result "shows that 
summer pruning has checked decidedly the growth of the trees as regards 
total amount of new wood produced." In general the authors concluded that 
in this experiment, summer pruning has checked tree growth and has delayed 
and decreased fruit production. Other experiments on trees five and six years 
old showed that "on young trees bearing their first crops suuimer pruning 
has reduced both vigor and fruitfulness." 

These results are not at all out of harmony with the general ideas expressed 
regarding dormant pruning. The thinning out of the branches in summer 
in all probability removed more in the way of potential fruit-bud area, stored 
nutrients, and the potential carbohydrate synthesizing area, than was com- 
pensated by admitting light and air into the remaining leaves and branches. 
Naturally a decreased total growth should be expected since it is also quite 
likely there was less available nitrate and moisture at the time of summer 
pruning as compared with the amounts present earlier in the season. The 
greater average length of terminal growth in the heavy dormant and the 
summer- and winter-pruned trees is not out of keeping with the general idea, 

25 



but as the authors themselves pointed out, this does not mean greater total 
growth, but rather the contrary. In fact, quite a point is made of the fact 
that lightly pruned trees showed a strikingly greater increase in trunk 
diameter, branch diameter, size of top, and total annual growth than those 
which received annual heavy dormant pruning. This result could readily 
be explained as the result of limiting the available carbohj^drates in the 
pruned trees. The moisture and nitrate conditions in the soil would not be 
materially changed by the mere removal of branches in itself, and if these 
were in excess of what would be utilized in increasing growth in the heavily 
pruned tree because of the limiting of the carbohydrates, then in the unpruned 
tree where such limit had not been imposed, total growth should be greater. 
If, however, the carbohydrates synthesized were in excess of the amount which 
might be utilized in simple vegetative extension, it might be expected that the 
character of growth would be progressively changed toward the reproductive 
type, as already pointed out. 

It is in experiments of this kind that the value of the study of the parts 
remaining after pruning, and the conditions and changes induced in them 
becomes apparent and are of even greater importance than what has been 
removed. Any attempt to measure vigor by growth response alone is unsafe. 
One of the greatest hindrances to advance in the study of the whole pruning 
problem has been segregation of growth, blooming and fruiting responses as 
if they belonged in different categories or were due to antagonistic fundamental 
causes. It seems much more helpful to an understanding of the problem to 
regard these responses as being due not so much to many distinct and separate 
causes, but rather to modifications or different combinations of a few, often 
closely associated or even inter-dependent. 

Some recent work reported by Gardner (11) deals with a somewhat different 
phase of summer pruning in apples. The work was done on young trees, not 
yet in bearing. The summer pruning consisted of a more or less severe heading 
back and thinning out in early summer, removing from 55 to 78 percent of the 
season's growth. The winter pruning of these same trees removed from 53 
to 72 percent of the late short growth formed for any particular year. From 
the winter-pruned trees 64 to 79 percent of the growth of any current year was 
removed. Some trees were unpruned. This type of summer pruning generally 
results in a putting forth of branches below the cut. These branches may 
attain a length of but a fraction of an inch or of many inches before the dormant 
season. If not of such length that they would interfere with the future ideal 
form of the tree, these shoots are not headed back in winter. If this secondary 
growth is profuse, it is often thinned out. Evidently this type of pruning is 
not quite the same as that reported by Batchelor and Goodspeed or by 
Alderman and Auchter. 

'•The data relating to shoot growth indicate that on the average the un- 
pruned tree increases in size a little more rapidly than the trees that are 
winter pruned only, or that are both winter and summer pruned. Its average 
annual shoot growth is less but it loses none of this by pruning and hence its 
net increase is greater. Broadly speaking there is but little difference in 
increase in size between trees that are winter pruned only, and those that are 

26 



both winter and summer pruned. The summer-pruned trees lose more shoot 
growth from pruning, but they produce nearly enough more to compensate 
for the additional loss." 

The greater size of the unpruned tree is in keeping with the results of 
Alderman and Auchter. The same suggestions as were made on their ex- 
periments are entirely applicable here. 

"While there is considerable variation between individual trees in the 
units of shoot growth they made in 1915 for each unit of 1914 shoot growth, 
there is shown no general tendency for the more severely pruned trees to 
produce more shoot growth for each unit of last year's growth than the less 
severely pruned trees. In fact, the average for the varying degrees of severity 
of pruning shows a slight tendency in the opposite direction. In other words, 
the evidence tends to show that at least in the case of young apple trees that 
have not yet produced many spurs, the amount of shoot growth they produce 
one season is nuich more closely correlated with the amount they made the 
preceding season than with the amount removed by winter pruning." 

"Study of the data presented indicates that on the average there is little 
or no relation between the severity of the early summer pruning given these 
trees and their subsequent response in shoot growth. Individual trees of any 
of the varieties might be selected for comparison that would seem to show 
that heavy early summer pruning results in a more rapid shoot growth than a 
lighter summer pruning. Conversely other individuals might be selected that 
would seem to indicate an opposite tendency. The averages, however, clearly 
show that amount of later summer -shoot growth following the summer priming 
here described is much more closely correlated with the amount of early shoot 
growth already possessed by the tree at the time of summer pruning than 
with the pruning itself. This would indicate that while on the average early 
summer pruning, like winter pruning, does not check rate of shoot growth, it 
results in a check to increase in size of tree because rate of growth is not 
accelerated; and that the heavier the summer pruning the greater is such a 
check. Attention is called to the fact, however, that the early summer 
pruning did not check the increase in size of the trees (as measured by shoot 
growth) to a degree greater than a correspondingly heavy winter pruning." 

An examination of the actual figures upon which this statement is based 
shows some wide departures from this general conclusion; so wide in fact that 
it is questionable if it is safe to venture an explanation of the results expressed 
only as a general average. It is essential that something more be known 
regarding the condition of the individual trees and branches as well as their 
length. Professor Gardner has told the writers that in his experiments the 
degree or state of maturity of the branches is a very great factor in determining 
response from this type of summer pruning. Now degree of maturity is really 
another way of expressing the evident difTerences resulting from different 
conditions of nutrition. Since for the purposes of this discussion the main 
interest centers in the nitrate, moisture, and carbohydrate conditions, and 
since no determinations of these substances are at hand, it is only possible to 
offer conjectures as to the possible causes of the results recorded. The relative 
state of development of the several trees or branches is an indication of the 
relative amounts of the substances mentioned which are present or available. 
How these influence growth has already been pointed out, but a few additional 
examples may be mentioned here. Now a branch which is very vigorously 
vegetative at the time of heading back is in itself an indication that it is 
receiving these nutrients in the proportions which produce such growth, and 

27 



on the other hand one which has made little vegetative extension, and has 
perhaps already developed a terminal bud indicates totally different pro- 
portions. What the response of any branch or tree will be after heading back 
will depend upon how these relationships are changed. Such heading back 
during the active growing season will exert its greatest limiting influence in 
carbohydrate synthesis, in much the same manner as does defoliation. The 
conclusion naturally follows that if the carbohydrate supply were decreased 
below the amount that could be utilized in maximum vegetative extension, 
considering the amounts of other compounds present, then growth would be 
decreased. If on the other hand the moisture-nitrate relations were such 
that there was not an active vegetative extension, but a surplus of carbo- 
hydrates (simple or complex), then a moderate heading back, which would 
tend to remove some of the latter, would result in a vegetative response until 
balanced relations were again restored. But as stated, if such heading back 
were so extensive that carbohydrate starvation effects were introduced, then 
vegetative activity would not result because of that fact itself, no matter what 
the nitrate-moisture conditions. In similar manner the entire range of results, 
already ascribed to the nitrate-moisture-carbohydrate relationships, might 
be expected. Actual experiments bear out such expectations remarkably well. 

Several other results reported by Gardner are of interest. All may be 
interpreted on the general hypothesis previously stated. "There seems to 
be a close correlation between increase in trunk circumference at any period 
during the summer and the leaf area possessed by the tree at that particular 
time." It should be remembered that young actively growing trees were 
used in the experiments. 

"Summer pruning of the type described affords a direct stimulus to fruit- 
spur formation. Some of the buds on the basal portions of the shoots that 
are left after the summer pruning almost invariably grow out into fruit spurs 
during the latter part of the summer. Those that remain dormant during 
the latter part of the summer are just as apt to develop into spurs the following 
year as similarly situated buds on shoots that are not summer pruned. 

"The later summer shoot growth of the summer-pruned trees is very 
productive of fruit spurs the season following its formation. A high percentage 
of its buds develop into spurs. Herein, apparently, lies the chief gain in fruit- 
spur production from the summer pruning. On the trees that are winter- 
pruned only, there is no growth to correspond with it. There is little or no 
relation between the severity of the summer pruning and the number of spurs 
to each unit of shoot length that remains." 

The outstanding facts of particular interest in these experiments are that 
the winter- and summer-pruned trees are very similar in the amount of growth 
accumulated, and that the summer-pruned trees produce larger numbers of 
fruit spurs, more in fact than those which have been winter pruned only. 
That the unpruned trees average greater total growth than those pruned, is 
another instance of greater accumulations through non-removal of any reserve. 
For the most part the type of summer pruning practiced removes only the 
terminal portions of the branches, the portion which in active growth, as most 
of these branches are at the time, contains least of the storage carbohydrates, 

28 



if there are any present. But since such a pruning does remove considerabe 
synthesizing area, it may prove seriously devitalizing in its effects. 

That there should be increased fruit spur formation on the summer-pruned 
trees is in accord with the general ideas expressed, since the new growth is 
only slightly or not at all cut back. There would be little or no removal of 
stored materials, so that the adjustment for fruit buds is more quickly estab- 
lished. (It should be borne in mind, however, that fruit spurs and fruit buds 
are not one and the same thing, and that the mere development of fruit buds 
does not necessarily mean fruit development.) 

Magness (31) has also called attention to the fact that in this method of sum- 
mer heading "the form of the summer-pruned shoot, which allows many axillary 
buds to be left at the time of the following winter pruning, accounts for the 
greatly increased number of spurs in trees that have received regularly an 
early summer heading back." In a later report on defoliation experiments, 
Magness (32) gives more concrete evidence bearing on the cause of such increased 
fruit-spur production. His summary is so suggestive that it is worth repeating 
in full: 

"The study of the relation of fruit-bud and leaf-bud formation and develop- 
ment of leaf area, as shown by the results following the removal of leaves, may 
be summarized as follows:. 

"1. Fruit-bud initiation will not take place, and fruit buds will not form 
in most varieties in the absence of a fair amount of leaf area in the tree. 

"2. Leaf area in one part of the tree will usually not supply food material 
to the buds in another part to the extent necessary to cause them to become 
fruit buds. Defoliating one-half of a tree has little influence upon the un- 
defoliated portion, but that part which is defoliated functions as it would if 
all the leaves had been removed from the whole tree. 

"3. Food material stored in the tree through the dormant season is 
apparently stored largely in the tissue adjacent to the leaves in which it was 
manufactured. This is shown by the fact that the defoliated portion of a 
tree does not develop as strongly and well diu-ing the spring following the 
treatment, as does the undefoliated portion. 

"4. Removing the same number of leaves, without any pruning, has 
practically the same effect upon the fruit-bud formation for the immediate 
year following, that a summer pruning, removing leaves from the same position 
would have. 

"5. Buds on one-year wood, in areas from which the leaves have been 
removed are slower in starting out into growth, and make a weaker growth 
the following spring than do other buds on the same shoots not defoliated 
This is more noticeable in some varieties than in others. 

"6. One shoot seems to be very largely independent of other shoots about 
it so far as fruit-bud formation is concerned. It is apparently largely de- 
pendent upon its own leaves for nourishment. 

' 7. Removing leaves from individual spiu's tends to prevent the formation 
of fruit buds upon those spurs, although it does not entirely check the develop- 
ment of flower parts. 

"8. On those spurs which form fruit buds, notwithstanding defoliation, 
the blossoms are, on the average, considerably later in opening in the spring. 

"9. Axillary buds of the Wagener seem to be almost entirely dependent 
upon the immediate subtending leaf for the carbohydrate supply with which 
they are nourished. Removing the subtending leaf entirely prevents fruit-bud 
formation. Buds so treated either remained entirely dormant during the 

29 



following growing season or pushed out into very weak growth. Very few of 
them showed a development approaching normal. 

"10. Microscopic examination of buds, both defoliated and undefoliated, 
taken at intervals during the summer, show little influence of the defoliation 
so far as development is concerned. No buds were studied that were taken 
later than September 12. 

"11. There is very decided decrease in the number of calcium oxalate 
crystals deposited in the tissues of defoliated as compared to undefoliated 
buds. This may be indicative of a small supply of soluble carbohydrates and 
general slow metabolism in the bud tissue. 

"12. Injury to the bark on the trunk of the tree very greatly stimulated 
fruit-bud formation. This injury brings about very different conditions of 
nutrition in the tree from those produced by defoliation, for by preventing 
the normal flow of elaborated foods to the roots, the supply in the top of the 
tree is greatly increased by the injury of the bark." 

The evidence as to the influence of carbohydrates on fruit-bud formation 
is particularly direct. The extremely close relation between the behavior of 
any bud relative to its immediate leaf area emphasizes such an influence still 
further, and is of great practical significance. It is unfortunate that no direct 
measurements of the various nitrogenous compounds are available, but it 
should be recalled that, for the most part, young vegetative trees were used, so 
located that there was a copious supply of soil nitrates. One tree of the 
Glowing Coals variety which had a severe trunk injury developed a little 
more than one-third as many fruit buds on the defoliated half as on the non- 
defoliated half, though the former produced much weaker bloom clusters the 
following spring. Magness has suggested that the conditions of nutrition in 
this tree caused an initiation of floral primordea somewhat in advance of the 
defoliation because of the relation of the elaborated foods in the tops. This 
is no doubt true, and the elaborated foods were probably carbohydrates for 
the most part. Of course this behavior resembles that of artificially girdled 
individuals, but the contrast in performance of the defoliated and non- 
defoliated halves bears out the general conclusion even more clearly. 

One other set of results reported by Drinkard (7) is particularly significant, 
when examined from the viewpoint previously expressed regarding growth 
behavior and fruit production. Some of his conclusions together with a 
suggested analysis follow: 

1. "Spring pruning of the branches of the trees at the time of growth 
resumption had a tendency to discourage the formation of fruit buds, but there 
was apparent stimulation of wood growth in the trees." 

An explanation for this result has already been given. The apparent 
stimulation resulting from severe heading back is an indication that nitrogen 
rather than carbohydrates was a limiting factor to vegetation. 

2. "Summer pruning of the branches of the trees the latter part of June, 
when fruit buds normally begin to show differentiation, checked wood growth 
the year in which the summer pruning was done, and greatly stimulated the 
formation of fruit buds as was shown by the bloom and crop of fruit the fol- 
lowing year." 

Without more complete data on the exact location of fruit buds and the 
full behavior of these trees, a complete explanation of the results is impossible. 
Still it is interesting to note some of them. Compared with the check trees 
and the spring- and fall-pruned trees, the average circumference of these 

30 



summer-pruned trees was less, the number of fruit buds formed was not greatly 
in excess of the checks, though decidedly greater than the spring-pruned trees. 
It may be suggested that the carbohydrates were present or being manu- 
factured in proportions relative to the available nitrogen, sufficient for copious 
fruit-bud initiation and development in those trees which received no pruning 
treatment. If so, then an early spring pruning would tend to reduce these 
from the standpoint of storage and subsequent synthesis. At this time, also, 
soil moisture and nitrates could be expected to be somewhat higher than at 
the time of summer pruning. The natural growth expression would be 
vegetative, provided that lack of carbohydrates were not a limiting factor, and 
the results indicate that they were not. It certainly would have been possible 
to make them so. A pruning given later in the summer would likewise remove 
some stored carbohydrates and of course synthesizing area, but at that time 
soil nitrates and moisture were probably relatively less so that a strong 
vegetative response would not be anticipated. Increased fruit-bud formation 
over the checks would be expected in this particular case only if the carbo- 
hydrate supply were relatively greater, which might have been the case, since 
the amount of leaf area removed may have been compensated by the admission 
of more light to the parts remaining, and by the new leaves developed. Such 
carbohydrates as were synthesized were not used up in vegetative extension, 
since these trees made very short growth in annual shoots. This is a par- 
ticularly interesting case in which it would be extremely desirable to know 
something of the relative proportions of the several' substances under con- 
sideration. Under the present circumstances they can only be surmised. 
These suggestions should be considered in connection with the next point. 

"Root pruning on April 23, at the resumption of growth in the absence of 
spring pruning, did not give as much stimulation to fruit-bud formation as 
the same treatment applied at later dates. Apparently this was too early 
for the full effects to be felt by the trees. Root pruning when the foliage was 
fully developed, and when the fruit buds began to become differentiated, in 
the absence of spring pruning of the tops, produced very marked stimulation 
in fruit-bud formation. At these three times the treatment retarded wood 
growth and foliage development in the current and succeeding year and the 
trees suffered from the treatment. 

"Severe root pruning at the time of growth resumption in the spring 
(April 23), at the time the leaves were well developed (May 31), and at the 
beginning of fruit-bud differentiation (June 23), when accompanied by or 
preceded by spring pruning of the branches, produced some stimulation in 
fruit-bud formation. Another series of experiments showed that the spring 
pruning did much to off-set the effects of the root pruning. The root-pruning 
treatment retarded wood growth in the current and succeeding year; the leaf 
area of the trees was reduced and the trees showed injury from the treatment.'' 

The results expressed in the two preceding paragraphs can best be analyzed 
together. A root pruning would be expected to reduce the intake of moisture 
and of mineral nutrients including nitrates. Of course the earlier in the season 
performed, the earlier some result would be produced in the top, though the 
results might not be quite the same under the two conditions. A root pruning 
when the foliage is fully developed and the fruit buds are beginning to become 
differentiated would mean decreased moisture and nitrate intake, whereas 

31 



carbohydrate synthesis would continue, assuming of course that such pruning 
is not so severe as to result in actual death of the tops. Without sufficient 
moisture and nitrates to utilize the carbohydrates in forming other compounds 
or in vegetative extension, they would tend to accumulate, with the resultant 
types of expression of vegetation and fruiting already enumerated from scarcity 
to marked fruit-bud production, even to the suppression of fruit-bud pro- 
duction, fruiting, and vegetation. On this basis it readily follows that, other 
conditions of root pruning and the like being the same, a spring pruning of 
the branches, which would decrease the materials already in storage and to a 
degree the subsequent amount of foliage developed, should tend to influence 
fruit-bud formation to the same extent that it modifies the relations of the 
carbohydrates to the moisture and nitrates. In the experiments under 
consideration fruit-bud formation for the most part was greater when the root 
pruning was not accompanied by branch pruning, but not necessarily so. 
Theoretically there .should be a point where fruit-bud formation on root- 
pruned branch-pruned trees should be relatively greater than on those which 
had been root-pruned only. That is, such a condition would exist when the 
root removal had so reduced the possibilities of absorption that it would be 
necessary to decrease the carbohydrates in proportion to the nitrates in order 
to promote growth. In the scheme already proposed this would mean a change 
from the fourth to the third condition. Such a situation is actually indicated 
in the fruit-setting records in the experiments under consideration. It should 
be brought out also, that a branch pruning removes many buds likely to develop 
into fruit spurs, whereas these remain when no pruning is given, so that a 
comparison based on numbers of fruit buds only, seems hardly a just one. 

"Ringing at different seasons when accompanied or preceded by spring 
l)runing of the branches produced no noticeable stimulation of fruit-bud 
formation. 

"Ringing at the time growth was resumed in the absence of spring pruning 
did not stimulate fruit-bud formation. The treatment was given too early. 
Ringing at the time the foliage was fully developed in the absence of spring 
pruning gave the best results; however, when the treatment was given at the 
time the fruit buds began to become differentiated, there was some stimulation 
of fruit-bud development." 

All these results would be expected in accordance with the general ideas 
proposed. There is little question that ringing would result in an accumula- 
tion of carbohydrates above the girdle, if they are being manufactured in 
excess of the amount utilizable in connection with the moisture and nitrates 
available. The same series of results would be expected as from root pruning 
or as from limiting the nitrate or nitrate and moisture supply. The situation 
is just the reverse of root pruning in which nitrate and moisture intake were 
limited through reducing the absorbing medium, but the same net result in 
the relation of carbohydrates to nitrates is gained by holding the carbohydrates 
in the top even though the root conditions are not mechanically changed. 
It would seem that if moisture and nitrate intake were not limited that growth 
should be little changed. A question may be raised here, however, in regard 
to the possibilities of moisture and general mineral intake when the carbo- 
hydrate supply is prevented from reaching the roots. There are reasons and 

32 



evidence for believing that the actual root extension is decidedly diminished 
by such carbohydrate limitation, and there is also quite likely a change in 
the power of the roots to absorb mineral nutrients. In any case such analyses 
as have been made do show an accumulation of carbohydrates above a girdle, 
generally in direct proportion to the severity of the ringing, whether there is 
also a limitation of nitrate intake remains to be determined. Thus a ringing 
when the trees were in full leaf might be expected to result in a more rapid 
accumulation of carbohydrates and in larger quantities than when such leaf 
surface were small or if the girdle healed before the leaf surface became larger. 
The relative amounts of moisture and nitrates available in the soil earlier or 
later in the growing season are also important factors to be considered. It is 
easily possible to make a girdling so severe that fruit-bud formation, blooming, 
fruiting, and growth are all seriously diminished. The whole range of growth 
responses resulting from the nutrient relations as previously proposed can be 
produced. 

"Stripping at different seasons when accompanied by or preceded by 
spring pruning, had no stimulative effect on fruit-bud formation. The effects 
of stripping were ofTset by those of spring pruning. Stripping at the three 
seasons already mentioned, in the absence of spring pruning stimulated fruit- 
bud formation uniformly." 

Stripping in its effects, is like ringing or girdling, except that it is less 
severe. What has been said for the latter will apply equally well to stripping. 



HISTORICAL 

There are many references in botanical and general agricultural literature 
dealing with a suggested relationship between plant responses and the avail- 
ability of elaborated or non-elaborated food. Some of these make no further 
explanations or suggestions regarding the particular nature of these foods, 
others roughly classify these compounds as mineral or organic nutrients, while 
still others fix upon specific compounds as related to specific responses. In ad- 
dition to specific references already mentioned in this article, several otiiers 
are of special interest. Up to the present time, at least, Klebs (21, 22, 23) has 
been one of the most active contributors to definite knowledge on this subject. 
He has worked with algae, fungi, and the higher plants. In the lower forms 
he has shown that by controlling the environmental conditions it was possible 
to cause the plants to remain in a vegetative condition, to produce zoospores 
or to reproduce sexually. He has demonstrated that much the same results 
could be secured in the higher plants as, for example, Sempervivum Funckii. 
(24). In a more recent paper (25) he has brought together the results of nu- 
merous investigations which have shown that the environmental conditions 
very largely determine whether a plant shall remain in a vegetative condition 
or become sexually reproductive. The controlling factors were found to be a 
reduction in the supply of nutritive salts (especially those which are nitro- 
genous) and an increase in the intensity of light, the efficiency of the illumina- 
tion being responsible for the formation of organic substances, such as carbo- 
hydrates. 

33 



It has been observed for a long time that most tropical trees show an altera- 
tion of growth and a rest period. This has quite often been attributed to some 
inherent heredity character. Klebs, (26) however, has regarded this condition 
as a result of external conditions acting upon the specific hereditary character 
of the plant. Each plant is supposed to possess certain hereditary possibili- 
ties in the way of expression of growth and reproduction, and the probable form 
which results will depend upon the surrounding conditions. Klebs has con- 
cluded that, since growth depends upon a large number of factors, any one of 
which may be a limiting factor, rest can be secured by suppressing any one of 
these factors to a minimum. Intense photosynthesis, producing a large supply 
of carbohydrates in case salts are not present in sufficient amounts, may result 
in rest. 

Crocker (5) in reviewing the foregoing work by Klebs, has stated the follow- 
ing: "It seems that Klebs has established his general contention of the dual 
determination of periodicity in these forms, but there are some minor concep- 
tions that are less happy. 

"He classifies all nutrient salts together as if they all have the same effect 
upon the course of development, while agriculturists have fully demonstrated 
that nitrates and phosphates in some respects have opposite efTects. He im- 
plies that salts have their effects mainly as nutrients (building materials), 
while the extensive work on antagonism probably deals with general physical 
or colloidal effects, and there is evidence that metallic ions are of importance in 
catalysis. Moreover, it is not yet known whether high nitrate supply induces 
vegetation and succulence through materials, (proteins, etc.) built from it, or 
through its lyotropic effects, and whether the partly contrasting effects of 
phosphates depend upon the first or second condition. Periodicity in salt ab- 
sorption which has been observed in trees and grains is also minimized. It 
seems evident that to get far back of the general proposition which Klebs has 
apparently proved, there is need of a careful study of internal conditions of the 
plant, anatomical, chemical, and microchemical, as well as the application (by 
injection or otherwise) of various salts and carbohydrates and products manu- 
factured from them to be sure of the effective agents." 

This summary very accurately defines the present status of the whole prob- 
lem and opens up the field of future attack. Some other references are of special 
significance in furnishing additional facts for interpretation of the nutrient 
relations in the plant itself. 

Fischer (8) has studied the starch and sugar transformations in a wide range 
of plants taken at various periods during the year. He did not differentiate 
between vigorous and non-vigorous individuals, but has distinguished between 
starch storeres and fat storers. He found that the stored starch underwent 
marked changes, and that such transformations are closely associated with the 
formation of glucose. 

Leclerc du Sablon (40) has investigated the carbohydrate reserves in the 
stem, root, and leaves of girdled and non-girdled pear trees three or four years 
of age. He found that by autumn there were greater reserves in the leaves but 
smaller amounts in the roots of the decorticated trees. Analyses of the stems 
indicated little difference. The chlorophyll, however, was less abundant in 
the leaves of the decorticated trees; such leaves were in general recognizable 
by their yellow color. It was suggested that there seemed to be a sort of regu- 

34 



lation of the assimilatory function; the products of chlorophyll assimilation 
not having their normal outflow thus encumbering the leaves, and causing a 
diminution in the production of chlorophyll. 

Hedrick (16) has reported ringing experiments with tomatoes and chrysan- 
themums. Commercially this practice was not a success. There was actually 
a decrease in the weight of fruit produced on the ringed tomato plants, and the 
root development of both the tomato and chrysanthemum plants which had 
been ringed was markedly decreased. 

Remy (38) has given results of the analyses of apple and pear trees used in 
fertilizer tests. Those trees from which nitrogen was withheld were markedly 
unfruitful. He has stated that a nitrogen content of at least 1.25% of the dry 
substance of the leaves is essential to fruit-bud formation, and that the flower- 
ing and fruiting condition is far more sensitive to variations in nitrogen supply 
than to potash, phosphoric acid, or lime. 

Petri (36)* has reported experimental studies on fruit setting in the olive. 
His observations are of particular interest. He has suggested that the abortion 
of the developing flowers and ovaries in the olive is due in large measure to a 
lack of sufficient supply of nitrogen in the plant tissues, and that this really 
constitutes a cause for sterility in that plant. A deficiency of nitrogen relative 
to the carbohydrate supply represents a stimulus to abundant formation of 
flowers, but if the available nitrogen supply goes below a certain limit, the 
flowers remain sterile because of incomplete development of the ovary. Lack 
of moisture in soil may be a cause of sterility, due to the lack of absorption of 
nitrates. His investigations are limited, but tend to bear out his conclusions. 
A later report (37) has confirmed and somewhat extended his former state- 
ments. He found that fertile branches of olive contained 2.119% to 2.370% N 
of dry weight, whereas those not setting fruit contained from 0.720 to 0.924%. 
"In normal conditions of vegetation the inception of the reproductive phase 
coincides with a relative prevalence of the products of assimilation over those 
that are derived in whole or in part from the mineral nutrients. Naturally 
this particular nutritive relation may be established both by an increase of the 
assimilatory function of the leaves and by a diminution of the absorbing roots." 
Petri has taken special pains to point out that the mere formation of floral 
parts does not necessarily indicate the capacity of any plant for fruit produc- 
tion, and that the nutritive relations for fruitfulness do not necessarily coin- 
cide with the extreme fluctuations under which "the simple differentiation of 
the reproductive organs" occurs. "The same deficiency of nitrogen which in 
many cases determines an abundant flowering, may also impede the develop- 
ment of the ovary when it goes beyond a certain limit. Likewise the deficiency 
of water in the soil may frequently stimulate the formation of abundant flowers 
and yet constitute a cause of arrest of the growth of the female organs." That 
sterility may be due to conditions of nutrition as well as heredity was also 
pointed out. 

Hartwell (15) has reported on work with potatoes and mangels in which he 
attempted to determine the effects of potassium in relation to starch assimila- 

*The writers are iadebted to Dr. Sophia H. Eckerson, of the Department of Botany of the 
University of Chicago, for a careful translation of the original articles by Petri. 

35 



tion. He has stated that, "A deficiency of available potassium in the soil was 
usually accompanied by an accumulation of starch in potato vines," and that 
"Many different factors, correlated in each case with retarded growth, were 
found to be associated with an accumulation of starch in the above-ground 
portion of plants." 

Hibino (20) has reported on his investigations in ringing. Among other 
things he found that in the ringed individuals above the wound there was an 
increase in organic and inorganic reserve materials. In the case of decortica- 
tion only these consisted of starch, reducing sugar, ether extract, and ash; if 
wood ringing was performed these were non-reducing sugar, proteins, crude 
fiber, and tannins. There were no estimates of nitrates, the total nitrogen de- 
terminations having been calculated to proteins. 

Recently the relation of nitrogenous fertilizers in connection with mottle- 
leaf in citrus trees has been receiving much attention. Briggs, Jensen, and 
McLane (4) have reported in connection with their investigations of this sub- 
ject that "groves which for some years had received only the 'complete' ferti- 
lizers in general use in the areas studied were badly mottled in all cases, so far 
as observed in these studies. This was also the case where sodium nitrate was 
used alone or as the principal fertilizer for some years. . . . No relation was 
found between the percentage of leaves mottled and the total nitrogen content 
in the soil in either the orange groves or the lemon groves studied." McBeth 
(33) has found that "mottled orange leaves have a higher moisture content 
than healthy leaves of the same age from the same tree. The nitrogen content 
of mottled leaves is also generally higher than healthy leaves. Extreme mot- 
tling is frequently associated with a high nitrate content, but the correlation 
is by no means an invariable one." The relation between nitrates and mottle 
leaf still remains to be established definitely. 



MATERIAL AND METHODS. 
Experimental. 

In the present work with tomatoes, we were interested mainly in a compara- 
tive study of the internal conditions in plants which were setting fruit, and 
those which were not, particularly with reference to the presence of total nitro- 
gen, nitrates, moisture, and carbohydrates, and the relations between them. 
Since our work was to deal largely with the conditions within the plant, we 
made little effort to determine the exact quantities of nutritive or other ele- 
ments in the soil in which the plants were grown, beyond a knowledge that the 
supply was abundant or restricted in any particular case. 

Materials. The tomato was selected as material for investigation because 
of the ease with which this plant can be handled and grown under green-house 
conditions, because it is clean cut in its fruit-setting responses to any set of 
conditions imposed, and because it is readily available in any quantity. 

36 



All the plants used, with the exception of one lot, were of the Lorillard 
variety and were raised from seed. The seeds were first sown in loam soil, the 
seedlings pricked off into individual two-inch pots containing rich potting soil 
and when they had made a height of some three or four inches, the most uniform 
plants were selected for transfer to any particular set of conditions which it 
was desirable to employ. For the most part the plants used were stocky, 
actively growing, and without external evidences of flower buds when they 
were selected for transplanting. 

For the sand cultures ordinary white quartz sand was used. This was free 
from organic matter but was not subjected to any particular treatment or 
washing before being used. It contained considerable c}uantities of iron. 
Without added nutrients the plants did not grow in it. This sand was used as 
a medium in which to grow plants subjected to a very low supply of nitrates. 
It was not desired in any case completely to eliminate them from the soil. A 
thin layer of cotton batting was put in the bottom of each pot before filling it 
with sand so as to prevent the latter from being washed through when the 
plants were watered. After filling the pots a porous battery cup was sunk into 
each, allowing about one-half inch to protrude above the surface of the sand. 
A large, flat cork was fitted into the opening. The nutrient solutions were 
poured into these cups and allowed to seep out into the sand. In this way the 
taking up of the nutrient solution by the pot itself and its later appearance as 
an efflorescense on the rim and sides, was almost entirely avoided. The roots 
of the growing plants formed a solid mat about the cups. 

The nutrient Knop's solution employed in connection with the sand cultures 
was made up as follows: 

A. Magnesium sulfate 2% 

Dibasic potassium phosphate 2% 

Potassium nitrate 2% 

B. Calcium nitrate 8% 

For use, equal parts of A and B were diluted one to seven with tap water and 
then mixed. Some precipitate was always formed, but this did not in any way 
seem to interfere in the use of the porous cups. Every three weeks the cups 
were scraped out with a scalpel and the accumulated sand and precipitate, 
which is always but little, dug into the sand about the plant. In some cases 
this was not done; not the slightest difference was observed in the plants in the 
two cases. 

When the plants were transferred to the pots containing sand, all the soil 
and adhering particles of organic matter were washed from the roots with great 
care. The plants were then placed in the sand about one-half inch deeper than 
they stood originally. This is desirable because a large part of the roots pre- 
sent at the time of transfer die back, but new ones are produced very quickly 
from the stem. 

The particular conditions for any particular lot or series of plants are given 
in connection with the analysis of the same, but there are some general condi- 
tions which will apply to all of them. No special precautions were taken re- 

37 



garding the general green-house conditions. So far as possible a temperature 
suitable for growing tomatoes was maintained, the light conditions of course 
varied with the season and external conditions, but care was taken that all 
plants in any lot or series were uniformly subjected to the same general condi- 
tions. The plants were grown in ordinary ten-inch to twelve-inch earthenware 
pots. Every pot, however, was placed in a granite-ware basin, which served 
the double purpose, first, of preventing the roots which came through the bot- 
tom of the pots from coming into contact with any soil in the benches on which 
the plants stood, or the leeching of any material from such soil into the pots, 
and second, it was possible to maintain a uniform condition of moisture in the 
several pots. For the most part our effort was to maintain, in each basin, 
when the pot was in it, a depth of about one inch of water. Of course imme- 
diately after watering this level was often higher, and sometimes it was a trifle 
lower; but the soil was not permitted to become dry in any case, except in the 
experiment where the soil was intentionally allowed to dry out. Water from 
the Chicago Municipal supply was used throughout all the experiments and in 
making up the nutrient solutions. 

Chemical. 

Sampling and Preservation of Samples. In order to obtain uniform samples 
in so far as it was possible, a number of plants were selected from any given lot 
which was to be sampled. After cutting the plants off just above the surface 
of the ground the leaves were removed, those from the upper half being kept 
separate from those of the lower half of the plant. The leaves were then cut 
into pieces about two inches long, and 100 grams weighed out for each sample. 
The stems were then cut into two-inch pieces and weighed. The samples were 
placed in large wide-mouthed glass-stoppered bottles and taken at once to the 
laboratory. 

Enough 95% alcohol was added to each sample to insure a concentration of 
about 75%. In all cases except the first few lots of samples 0.25 gr. of precipi- 
tated CaCOawas added in order to neutralize any acids which might be present. 
After heating for one hour on a steam bath at 70° to 75° C. the samples were 
placed away until they could be analyzed. 

It might seem as though there would be sufficient loss of moisture to cause 
error from the time the samples were cut up until they were weighed, but 
Table I will illustrate that such was not the case. In Table I, samples 1, 2, 
and 3 were taken without cutting the plants and samples 4 and 5 were weighed 
from a composite of the plants which had been cut into two-inch pieces. The 
moisture in sample 6 is calculated from the determinations of series M, upon 
the basis that there was twice as much green weight in the leaves as in the stem, 
a ratio which was noted when the samples were taken. The other samples 
were taken from the same lot and at the same tims as series M. 

Extraction of the Samples. After the samples had been allowed to stand for 
at least several weeks, the alcohol extract was poured off and filtered into a liter 
flask. The residue was then transferred to a pyrex beaker. Small amounts of 

38 



Table I. — Showing the Determinations for moisture in Whole^Plants 
AND Those Cut into Small Pieces. 



Sample 


Character of 
Material 


Percentage 
of moisture 


1 .... ... 


Whole plants 

Whole plants 

Whole plants 

Cut into 2-inch pieces 

Cut into 2-inch pieces 

From sample extracted 

Series M 


91 17 


2 


91 06 


3 . . . . 


91 40 


4 


91 61 


5 


91 65 


6 


91 63 







warm 80% alcohol were added and allowed to cool and then filtered into the 
liter flask. After repeating this operation until there were about 900 c.c. in 
the flask the residue was dried upon a steam bath and then transferred to a 
small weighed beaker. All of the extract remaining in the original beaker was 
transferred to the filter and the filter paper was washed carefully. The ex- 
tract in the flask after coming to room temperature was made up to a liter and 
then stored away in a tightly stoppered glass bottle. After the residue was 
air dried it was weighed, ground finely in a mill, and then weighed out into 
one-fifth sample and one-twentieth sample aliquots. 

Total Nitrogen. Fifty cubic centimeters of the extract, representing 
V20 of the original sample were placed in a Kjeldahl flask and placed upon a 
steam bath to drive off the alcohol. An aliquot of the residue representing 
V20 of the sample was then added and the total nitrogen determined by the 
Kjeldahl method modified to include nitrates. 

Nitrate Nitrogen. The nitrrte nitrogen was determined by a modification 
of the Schulze (42) method very similar to that used by Mitchell, Shonle, and 
Grindley (34). The method was checked up with a sample of potassium ni- 
trate of known strength. 

Carbohydrates. Two hundred cubic centimeters of the extract represent- 
ing 1/5 of the sample were placed in a beaker and the alcohol driven off upon a 
steam bath. An aliquot of the residue representing 1/5 of the sample was 
placed upon a filter paper and extracted with 200 c.c. of warm water (30°-40°C.) 
in successive small portions. Such an extraction completely removed all the 
free-reducing substances and sucrose. The extract of the residue was used to 
transfer the extract from the alcohol solution to a250 c.c. volumetric flask. The 
extract was then neutralized when necessary with NaOH and cooled to room 
temperature. The solution was cleared with just sufficient basic lead acetate, 
then made up to volume and without standing longer than to allow the precipi- 
tate to settle, was filtered through a dry filter paper into a dry vessel. Two 
hundred cubic centimeters of the filtrate were placed in a 250 c.c. volumetric 
flask and sufficient saturated Na2S04 solution was added to precipitate any 
very slight excess of lead. This solution was made to volume and after stand- 
ing until the lead was completely precipitated was filtered through a dry filter 
paper into a dry flask. This solution was used for the determination of free 
reducing substances and the easily hydrolyzable non-reducing disaccharides 

39 



(Bucrose*) . The residue from the water extraction was used for the determina 
tion of polysaccharides (starch*). 

Free-Reducing Substances . Twenty-five or fifty cubic centimeters of the 
cleared extract were used for the determination of the free-reducing sub- 
stances. 

Sucrose. Seventy-five cubic centimeters of the extract were placed in a 
100 c.c. volumetric flask. Five cubic centimeters of HCl(sp.gr. 1.19) were added 
slowly and then the flask was placed in a water bath at 70° so that the solution 
reached 65° to 70° at the end of 33^ minutes and was kept at 69° C. for6H min- 
utes longer. The flask was then removed, cooled, neutralized, cooled to room 
temperature, and made up to 100 c.c. After being filtered through a dry filter 
paper into a dry flask 25 or 50 c.c. were used for the determination of the reduc- 
ing power. 

Polysaccharides. The residue from the water extraction was boiled with 
150 c.c. of water and 15 c.c. of HCl (sp. gr. 1.125) in a two-liter flask with a re- 
flux condenser for two and one-half hours. After neutralizing to litmus with 
NaOH the solution was transferred to a 250 c.c. flask. After clearing with 
basic lead acetate and deleading with Na2S04, 25 c.c. of the solution was used 
for the determination of the reducing power. 

The reducing power of all of the carbohydrate solutions was determined by 
a combination of the Munson and Walker method and the Bertrand method. 
The reduction was carried out under the conditions of the Munson and Walker 
method and the tables of this method were used (43). The determinations of 
the amount of reduced copper were carried out by the Bertrand method. 

The results have all been calculated and expressed as dextrose. While this 
does not give absolute results for the different carbohydrates, such results are 
none the less comparative. Any reliable method for a more definite differen- 
tiation of the carbohydrates would have consumed so much time that it would 
have been impossible to cover so wide a range of material. It seemed wiser, 
therefore, to make a general survey now and to defer a more minute study until 
a later time. 

General Statement. The free-reducing substances represent the total re- 
ducing power of the extract before hydrolysis, expressed as dextrose. Sucrose 
represents the increase in reducing power due to the hydrolysis under the con- 
ditions given for the determination of sucrose. The results are expressed as 
dextrose. While this may not give absolute results for the amount of sucrose 
it does give the relative amounts of sucrose or substances which are hydro- 
lyzed with the same degree of ease. A sample of pure maltose was sub- 
jected to the same method of hydrolysis and no measurable increase of reduc- 
tion due to the hydrolysis was detected. Starch is expressed in terms of dex- 
trose. Although the method used for the determination of starch is not abso- 
lute and includes any polysaccharides which are hydrolyzed under the condi- 
tions imposed with the production of reducing substances, it should be kept 
in mind that the term is used with that significance. The substances included 
in addition to the starch are those which are hydrolyzed with about the same 

*The terms "sucrose" and "starch" are used throughout this discussion with the significance indi- 
cated in the paragraphs under the "general statement." 

40 



degree of ease. Micro-chemical teste show an abundance of starch grains 
where the determinations for starch are high and scarcely any starch where 
the quantitative methods show very low amounts. It is quite probable that 
the polysaccharides hydrolyzed by this method are made up of starch in a 
large part. 

Moisture and Dry Weight. One hundred cubic centimeters of the alcohol 
extract were evaporated to dryness upon a steam bath and then dried to con- 
stant weight in a vacuum oven at 78°C. From this weight the total dry weight 
of the extract was calculated. The total dry weight of Vs of the residue was 
determined by drying under the same conditions as mentioned above. The 
moisture was then determined by difference. 

Microchemical. 

The principal substances tested for microchemically in all the experiments 
were free-reducing substances, starch, and nitrates, to a lesser extent deter- 
minations of calcium, potassium, oxalates, and chlorides were also made. All 
the analyses were made immediately after cutting the fresh material and bring- 
ing it into the laboratory. All tests were made in triplicate, at least. 

The following were the three principal tests employed: 

Free-reducing Substances. Fliickiger's Reagent made up of a minute quan- 
tity of copper tartrate placed in a drop or two of 15% to 20% NaOH was used. 
When the copper tartrate was completely dissolved and mixed with the sodium 
hydrate, thin sections were cut from the material to be tested, immediately 
placed in the solution, and a cover glass added. The preparations were then 
placed on a water bath at about 90°C for one hour. Comparisons were based 
on the relative number and size of the dark brown granules of copper oxide 
precipitated. 

Tests based on osazone formation were entirely unsatisfactory for the to- 
mato tissue. 

Nitrates. The reagent used was made by dissolving 0.1 grams diphenyla- 
mine in 10 grams 75% sulfuric acid. Fresh sections were placed on a slide, 
covered, and the reagent run in from the side of the cover. A blue color indi- 
cated the presence of nitrates. Very satisfactory comparisons were obtained 
by noting the intensity of the coloration. 

Starch. The well-known test, iodine-potassium iodide solution was em- 
ployed, and the peculiar granular nature of the starch noted. 

Anatomical Methods. 

For the anatomical studies both fresh and preserved material was used. 
Some of the stems were cut in parafine though for the most part material hard- 
ened in alcohol was cut sufficiently well on a sliding microtone without previous 
imbedding of any kind. For the more detailed studies the material was stained 
in Safranin and Griibler's Lichtgriin and mounted in balsam. 



41 



PRESENTATION OF DATA 
Chemical. 

Experiment II. The plants from which samples of Series A and E were 
taken were of the variety Ponderosa. They were grown in ordinary greenhouse 
soil in 2J^-inch pots, and at the time of transplanting were about five inches 
tall, slender, somewhat yellowed, and showing flower buds. 

On June 14, 1916, they were transplanted in the greenhouse to a ground bed 
about two feet in depth, of fresh cow manure which contained considerable hay 
and straw but without the admixture of any soil whatsoever. Ordinarily these 
conditions would be considered wholly unfitted for the growing of tomato 
plants, but within several days, the young plants took on a healthy green color 
and began to grow vigorously, though most of the blossom buds fell off before 
or immediately after blooming. 

The samples constituting series A were taken July 25 at 9:30 a. m. on a clear 
day. The plants were then about four feet high, had a good green color, were 
flowering fairly well but had failed to set fruit. 

The samples constituting series E were taken September 8, at 9:30 a. m. 
during fairly clear weather. The plants were still distinctly vegetative, about 
five to six feet high, beginning to turn somewhat yellow, and although they 
blossomed freely, scarcely any fruit was produced. The analyses are given in 
Tables II, III, IV, and V. Because the variation in dry matter of the plants 
grown under different conditions and in different parts of the plant is great, it 
seemed wise to give the results calculated to both the dry weight and to the 
green weight. 

These plants of this series were high in moisture, total nitrogen, and nitrate 
nitrogen and low in total dry matter, sucrose, and polysaccharides, and fairly 
high in free-reducing substances. In the stem, going from the top to the bot- 
tom, the total nitrogen decreased and the polysacchrides, free-reducing sub- 
stances, and total dry matter increased. In the leaves this relation of total 
nitrogen and nitrate nitrogen to free-reducing substances is the opposite, but 
with the polysaccharides the same relation holds as was found in the stems. 



Table II. — Series A. 
All results computed to a dry-weight basis except moisture and dry matter. 



Material 


Upper 

First 

deter. 


leaves 
Second 
deter. 


Lower leaves 


Upper 


stems 


Lower stems 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


Moisture 


% 

90.11 

9.89 

5.02 

"\M 
0.00 
6.90 


% 

'5.06' 

'r97' 
0.00 




% 
91.25 

8.75 
3.36 

'2^21' 
0.00 
7.59 


% 

90.88 

9.12 

3.41 

2^73' 
0.00 


% 

93.29 

6.71 

1.81 

2.08' 
0.53 
7.90 


% 

'i'76' 

'2.20' 
70 
7.90 


% 

91.70 

8.30 

1.74 

i.'ii' 

8^43' 


% 


Total Nitrogen 

Nitrate nitrogen 

Free-reducing substances. 

Sucrose 

Starch 


i.78 
1 Jl 
8^26' 



42 



Table III. — Series A. 
All results computed to a green-weight basis. 



Material 


Upper 


leaves 


Lower leaves 


Upper 


stems 


Lower stems 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


Moisture 


% 
90.11 
9.89 
0.496 

'b.m 

0.000 
0.682 


% 

'6!5o6 

'o'l94 
0.000 


% 
91.25 
8.75 
0.294 

'o;238 
0.00 


% 
90.88 
9.12 

0.00 


93.29 
6.71 
0.121 

0.139 
0.055 
0.5301 


% 

'o!ii8 

'0^147 
0.027 
0.5301 


% 

91.70 

8.30 

0.144 

0.092 

0^699 


% 




147 






Free-reducing substances. 

Sucrose 

Starch 


0.092 
0^685 



Experiment V. For this experiment seeds of the Lorillard variety were 
sown July 29, 1916. The young plants when large enough to handle were trans- 
planted to a rich loam soil in 23/^-inch pots, watered as required, and forced 
along rapidly until they were from six to eight inches high. By September 1, 
the plants were thrifty and healthy and just beginning to show flower buds. 
On this date most of them were taken out of the pots in which they were grow- 
ing and the soil washed carefully from the roots. They were then transplanted 
to three different conditions of nitrogen supply. 

1. Those from which the samples of series G and B were taken were trans- 
planted to ten-inch pots containing a soil mixture of one-half clay loam, one- 
fourth sand, one-fourth well-rotted manure. They were given an abundance 
of moisture, and well exposed to the light. They grew rapidly, were dark green 
and succulent and produced many blossoms, most of which fell off soon after 
opening. 

Series G was collected on September 28 at 10:00 a. m. on a fairly clear day. 
At this time, the plants were about three feet tall, decidedly vigorously vegeta- 
tive and yet somewhat fruitful. The foliage was large and dark green, the 
stems of large diameter and succulent, particularly the upper two-thirds. 

Series B was collected on October 12, at 10:00 a. m. on a slightly cloudy day. 
These plants were still dark green and vigorous, had set a few more fruits than 
those in series G above, were somewhat taller, the foliage not quite so dark 
green and the stems were more firm and less succulent. 

Table VI. — Series G. 
All results computed to a dry-weight basis except vioisture and dry matter. 



Material 


Upper 


leaves 


Lower leaves 


Upper 


stems 


Lower stems 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


Moisture 


% 
91.45 
8.55 
5.58 
0.64 
3.27 
0.46 
8.40 


% 

'5.34' 
0.64 
3.30 
0.41 

8.46 


% 
91.64 
8.36 
4.03 
0.99 
2.20 
0.00 
6.13 


% 
'4.01' 

'2;i8' 

0.00 
6.04 


% 
95.06 
4.94 
3.77 
0.57 
3.16 
0.07 
6.43 


% 

■3!26' 
0.55 
3.15 
0.07 
6.64 


93.66 
6.34 
2.76 
0.73 
0.88 
0.00 

10.44 


% 





2.51 




0.71 


Free-reducing substances. 

Sucrose 

Starch 


0.80 
0.00 
10.64 



43 



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Table VII. — Series G. 
All results computed to a green-weight basis. 



Material 



Moisture 

Dry matter 

Total nitrogen 

Nitrate nitrogen 

Free-reducing substances. 

Sucrose 

Starch 



Upper leaves 



First Second 
deter. deter. 



91.450 
8.550 
0.477 
0.054 
0.279 
0.039 
0.718 



0.456 
0.055 
0.282 
0.0.35 
0.723 



Lower leaves 



First Second 
deter. deter. 



91.640 
8.360 
0.336 
0.083 
0.183 
0.00 
0.512 



0.3.35 

0^182 
0.000 
0.505 



Upper stems 



First Second 
deter. deter. 



95.060 
4.940 
0.186 
0.028 
0.156 
0.007 
0.317 



0.161 
0.027 
0.155 
0.000 
0,328 



Lower stems 



First Second 
deter. deter. 



93.660 
6.340 
0.201 
0.046 
0.055 
0.000 
0.661 



0.159 
0.045 
0.050 
0,000 
0.674 



Table VIII. — Series B. 
All results computed to a dry-weight basis except moisture and dry matter. 



Material 


Upper leaves 


Lower leaves 


Upper 


stems 


Lower stems 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


Moisture 


% 
86.77 
13.23 
3.31 
3.26 
0.00 
12.04 


% 

3^.30 
3.21 
0.00 
12.27 


% 
89.44 
10.56 
2.24 
3.66 
0.00 
7.00 


% 

i.u 

3.65 
0.00 
7.12 


% 
91.17 
8.83 
2.08 
8.06 
1.84 
7.37 


% 

2.07 
8.03 
1.88 
7.33 


% 
89.76 
10.24 
0.96 
6.67 
4.01 
8.54 


% 




1.16 


Free-reducing substances . 

Sucrose 

Starch 


6.65 
4.05 
8.41 



Table IX. — Series B. 
All results computed to a green-weight basis. 



Material 


Upper 


leaves 


Lower leaves 


Upper 


stems 


Lower stems 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


Moisture 

Dry matter 


% 
86.770 
13.230 
0.437 
0.431 
0.000 
1.593 


% 

0^436 
424 
0.000 
1.623 


% 
89.440 
10.560 
0.236 
0.386 
000 
0.739 


% 

0^226 
0.385 
0.000 
0.751 


% 
91.170 
8.830 
0.183 
0.711 
0.163 
0.650 


% 

0J82 
0,709 
0.166 
0.647 


% 
89.760 
10.240 
0.098 
0.683 
0.410 
0.874 


% 





0.118 


Free-reducing substances . 

Sucrose 

Starch 


0.681 
0.414 
0.861 



2. Those from which series H and C were taken were transplanted to twelve 
inch pots containing quartz sand. Each pot received 350 c.c. of diluted Knop's 
solution at each of five applications as follows: September 2, September 8, 
September 28, (after sampling), September 30, October 9. Following the 
transplanting the plants soon began to grow fairly rapidly, but the leaves were 
grayish green in color, stood out stiffly from the stems, felt firm and harsh 
rather than succulent to the touch; the stems were erect, small in diameter, 
tough, and scarcely at all succulent except perhaps at the apical one-sixth. 
There was an abundance of bloom and many of the earlier flowers set fruit 
readily, though the later ones failed to do so in as great proportion. 



45 



Series H was collected September 28 under the same conditions as series G 
above. At that time the plants were about two feet tall, blooming abundantly, 
and setting at least two-thirds of the blossoms, some of the larger young fruits 
were about one inch in diameter. 

Series C was collected October 12 at 10:00 a. m. on a slightly cloudy day. 
At this ti me the plants were still blooming abundantly but were setting only 
one-half or less of the blossoms, were more gray in appearance, the lower leaves 
slightly yellowed, and the stems more stiff and firm. In general, the plants 
could be characterized as only moderately vegetative. 

Table X. — Series C. 
All results computed to a dry-weight basis except moisture and dry matter. 



Material 


Upper 


leaves 


Lower leaves 


Upper 


stems 


Lower stems 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


Moisture 

Dry matter 


% 
88.01 
11.99 
2.31 
0.14 
3.10 
0.43 
11.25 


% 

'2^06' 
0.13 
3.21 
0.32 

11.25 


% 
89.68 
10.32 
3.16 
0.06 
0.75 
1.53 
12.20 


% 

'2;87 
0.05 
0.73 
1.77 

11.70 


Vo 
88.62 
11.38 
1.65 
0.07 
6.82 
3.15 
9.83 


% 

'i;48' 

0.07 
6.73 
3.51 
10.00 


% 
86.24 
13.76 
1.36 
0.036 
4.57 
4.58 
10.75 


% 
\.Z2 


Nitrate nitrogen 

Free-reducing substances. 

Sucrose 

Starch 


'4!54' 
4.37 
10.92 



3. Those from which series I and D were taken were treated exactly as 
Lhose in H and C except that potassium nitrate was omitted from the nutrient 



Table XL — Series C. 
All results computed to a green-weight basis. 





Upper 


leaves 


Lower leaves 


Upper 


stems 


Lower stems 


Material 
















First 


Second 


First 


Second 


First 


S econd 


First 


Second 




deter. 


deter. 


deter. 


deter. 


deter. 


deter. 


deter. 


deter. 




% 


% 


% ■ 


% 


% 


% 


% 


% 


Moisture 


88.010 
11.990 




89.680 
10.320 




88.620 
11.380 




86.240 
13.760 




Dry matter 




Total nitrogen 


0.277 


0.247 


0.326 


0.296 


0.187 


0.168 


0.187 


0.181 


Nitrate nitrogen 


0.017 


0.015 


0.006 


0.006 


0.009 


0.009 




0.005 


Free-reducing substances. 


0.371 


0.384 


0.077 


0.075 


0.776 


0.765 


0.623 


0.624 


Sucrose 


0.051 


0.038 


0.157 


0.182 


0.358 


0.399 


0.630 


0.601 


Starch 


1.347 


1.347 


1.259 


1.207 


0.669 


0.674 


1.479 


1.503 



solution and instead of calcium nitrate, one-half the amount was substituted 
with calcium chloride. The nutrient solution therefore was without nitrates 
except those contained in the water supply. 

Series I was collected September 28 under the same conditions as G and H. 
The plants were twelve to eighteen inches tall, yellowish except at the tips, the 
lower leaves having fallen or about to fall on many of the specimens, the stems 
comparatively small in diameter but distinctly firm and woody to the touch. 
There were no blossoms or fruit, though there was an occasional weak blossom 

46 



cluster only partly developed. Commonly the plants would be spoken of as 
distinctly sickly in appearance. 

Series D was taken at the same time and under the same conditions as series 
B and C. At that time the plants were little or not at all taller than on Sep- 
tember 28, light yellow, many were without lower leaves, the stems were more 
firm to the touch and practically no blossom clusters were present. 

Series F was made up of plants which had been left undisturbed in the small 
pots in which they were growing and collected for analysis September 8 at 10:00 
a. m. on a clear day. 

Table XII. — Series D. 
All results computed to a dry-iveight basis except moisture and dry matter. 





Whole plant 

First sample 


Whole plant 
Second sample 




First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


Moisture 


% 
85.11 
14.89 
0.93 
0.00 
6.41 
6.52 
21.04 


% 


% 
84.56 
15.44 
0.98 
0.00 
4.57 
3.98 
19.23 


% 








Total nitrogen . 












Free-reducing substances 

Sucrose 


6.43 


4.45 


Starch 


20.97 









Table XIII. — Series D. 
All results computed to a green-weight basis. 





Whole plant 
First sample 


Whole plant 
Second sample 




First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 




% 
84.560 
15.440 
0.151 
0.000 
0.706 
0.615 
2.973 


cr 
/o 


% 
85.11 
14.89 
0.138 
0.00 
0.954 
0.970 
3.133 


% 




















Free-reducing substances 


0.688 


0.957 






3.122 









Table XIV.— Series F, H and I. 
All results computed to a dry-weight basis except moisture and dry ynatter. 



Material 


Whole plant 
Series F. 


Whole plant 
Series H. 


Whole plant 
Series I. 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


Moisture 


% 
92.65 
7.35 
2.88 
0.52 
2.01 
0.00 
8.54 


% 

0^53 
2.15 
0.00 
8.40 


% 
90.12 
9.88 
3.00 
0.15 
0.88 
0.17 
4.06 


% 

"2:99" 
0.18 
0.79 
0.26 
3.99 


% 

85.95 

14.05 

1.78 

0.00 

4.01 

1.21 

15.66 

1 


% 


Total nitrogen 


1.70 i, 
0.00 


Free-reducing substances 


4.00 
1.20 


Starch 


15.70 



47 



Table XV. — Series F, H, and I. 
All results computed to a green-weight basis. 



Material 



Moisture 

Dry matter 

Total nitrogen 

Nitrate nitrogen 

Free-reducing substances. 

Sucrose 

Starch 



Whole plant 

Series F. 



First 
deter. 



% 
92.650 
7.350 
0.211 
0.038 
0.147 
0.000 
0.627 



Second 
deter. 



0.039 
0.158 
0.000 
0.617 



Whole Plant 
Series H. 



First 
deter. 



c/ 
90.120 
9.880 
0.296 
0.015 
0.086 
0.016 
0.401 



Second 
deter. 



0.295 
0.018 
0.078 
0.025 
0.394 



Whole plant 
Series I. 



First 
deter. 



% 
85.950 
14.050 
0.250 
0.000 
0.563 
0.170 
2.200 



Second 
deter. 



0.238 
0.000 
0.562 
0.168 
2.206 



Series G. The analyses show that compared with the other two series H 
and I the plants of series G were high in moisture, total nitrogen, and nitrate 
nitrogen, and, compared with series I, are low in free-reducing substances, 
disaccharides, polysaccharides, and total dry matter. It is difficult to com- 
pare with series H where the differences are not so marked because the whole 
plant was taken as a sample in the lattef case. In the stems of series G going 
from top to bottom there is considerable difference in total nitrogen and nitrate 
nitrogen. There is also an increase in polysaccharides and a decrease in free 
reducing substances. It is apparent, however, that the plants of series H are 
low in moisture, nitrate nitrogen, and total nitrogen and are higher in total 
dry matter. 

Series I. Compared with the vegetative plants of series G they are much 
lower in total nitrogen. The free-reducing substances, sucrose, polysacchar- 
ides, and total dry matter are very much higher than in series G. Here again 
no comparison can be made upon the different parts of the plant because whole 
plants were used to make up the sample. 

Series B. In composition the plants in series B resemble the plants of 
series G except that the stems of the latter are higher in moisture and total 
nitrogen and lower in disaccharides, and total dry weight. In the stems of 
the plants themselves in series B there is an increasing gradient from top to 
bottom in total dry matter, sucrose, and polysaccharides and a decreasing 
gradient in total nitrogen and free-reducing substances. In the leaves there 
is no such relation between nitrogen and carbohydrates. 

The plants of series C compared with series B were less vegetative and more 
fruitful. In the stems of series C there is a decreasing gradient from top to 
bottom in moisture, free-reducing substances, and nitrate nitrogen, and an in- 
creasing gradient in total dry matter, sucrose, and polysaccharides. The total 
nitrogen is about the same in the upper and lower portion of the stems. In the 
leaves there is no such relation between nitrogen and carbohydrates. 

Series D. Compared with series B the plants were low in moisture and total 
nitrogen and high in sucrose and polysaccharides. Nitrates are absent. Since 
whole plants were taken to make the samples, no comparisons can be made be- 
tween the different parts of the plant itself. 

48 



Series F. The analyses show that the plants were high in moisture and 
nitrate nitrogen and fairly high in total nitrogen. The free-reducing sub- 
stances and polysaccharides were low, and sucrose was absent. 

While not recorded for analysis it is worthy of note that at the close of this 
experiment a few pots containing plants which had received no nitrates still 
remained. To each of these, 100 c.c. of a one percent calcium nitrate solution 
was added. Within four or five days the stems of these plants began to turn 
green, the terminal leaves became darker green and expanded, and terminal 
axial growth was rapid. This result is of interest more particularly in indi- 
cating that the reason for the slow growth previously was the lack of nitrate 
rather than some other essential element or the presence of some harmful salt 
in the modified nutrient solution. 

Experiment VI. The seed for this lot of plants of the Lorillard variety was 
sown October 20, 1916. On October 30 the plants were transplanted to three- 
inch pots of rich, fertile soil and on December 11 the plants were transplanted 
to the three different conditions of soil nitrogen supply; namely, quartz sand 
without nitrogenous fertilizer, quartz sand with Knop's solution, and to a rich 
potting soil composed of clay loam one-fourth, sand one-fourth, well-rotted 
manure one-half. The analyses were listed under series J, K, and L. No 
analyses were finally made of the plants which were transferred to sand and 
given no nitrogenous fertilizers so they are not listed below. 

Series J is made up of plants collected about 2:00 p. m. December 13, 1916, 
which were still in the three-inch pots of rich soil. The day was clear. At 
that time the plants were growing vigorously, about four to six inches tall, 
dark green, sturdy and succulent, without visible blossom buds. It was hoped 
to use the analyses of these plants as a basis for study of variation in the later 
analyses of plants grown with large and small soil-nitrogen supply. 

Series K was collected at the same time and under the same conditions as 
series L. Following transplanting, the plants had been grown in the rich pot- 
ting soil noted above, but the moisture supply was limited. Instead of main- 
taining a constant supply in the granite-ware pans in which the pots had been 
placed, the pots were watered only at intervals as needs seemed to reciuire in 
order to keep them above the wilting point. The plants were about three to 
three and one-half feet tall, growing moderately vigorously, the foliage was large , 
and dark green. Each plant had two or three blossom clusters of good size and 
one to several fruits. Compared with series L, the plants were much the same 
except that they gave the general impression of being greener and more stocky 
in every way. 

Series L was collected February 16, 1917, at 2:00 p. m. on a clear day. The 
plants had been grown in twelve-inch pots containing quartz sand. To each 
pot had been added 350 c.c. Knop's solution diluted one to seven on each of the 
following dates— December 11, 18, January 8, 13, 22, 29. At the time of collec- 
tion the plants were from three to three and one-half feet tall, moderately vege- 
tative, the leaves large and green, somewhat drooping, those at the base some- 
what smaller and lighter in color, the lower two-thirds of stem firm, green, the 

49 



upper one-third succulent. There were several blossom clusters of good size, 
and two to five fruits to each plant, though a number of blossoms had fallen 
without setting. 



Table XVI. — Series J. 
All results computed to a dry-weight basis except moisture and dry matter. 





Whole plant 
First sample 


Whole plant 
Second sample 




First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


Moisture 


% 
93.44 
6.56 
3.36 
0.90 
1.77 
0.87 
12.98 


% 


% 
93.18 
6.82 
3.45 


% 


Dry matter 






Total nitrogen 






Nitrate nitrogen 






Free-reducing substances 


1.57 


1.79 
0.75 
13.13 




Sucrose 




Starch 


12.62 


13.20 



Series J. The plants were high in moisture and fairly high in total nitro- 
gen and nitrate nitrogen and low in free-reducing substances, sucrose, and total 
dry matter. 

Series K. Compared with series L, they are higher in moisture and in total 
nitrogen, but .slightly lower in sucrose, polysaccharides, and total dry matter. 

Table XVII. — Series J. 
All results computed to a green-weight basis. 





Whole plant 
First sample 


Whole plant 
Second sample 




First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


Moisture 


% 
93.440 
6.560 
0.2S2 
0.059 
0.116 
0.057 
0.851 


% 


% 

93.180 

6.820 

0,282 


% 


Dry matter 






Total nitrogen 






Nitrate nitrogen 






Free-reducing substances 


0.103 


0.122 
0.051 
0.895 




Sucrose 




Starch 


0.828 


0.900 



Table XVIII.— Series K. 

All results computed to a dry-weight basis except moisture and dry matter. 





Upper leaves 


Lower leaves 


Upper stems 


Lower 


stems 




First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


Moisture 


% 

89.06 

10.94 

4.03 

0.04 

3.06 

1.55 

15.12 


% 

3^96' 
0.04 
3.17 

14^49' 


% 
91.26 
8.74 
2.84 
0.09 
1.77 
0.92 
2.23 


% 

2^56 
0.13 

1.82 

2^08 


% 
93.16 
6.84 
2.52 
0.17 
11.30 
0.82 
5.41 


/o 

2^43' 
0.14 
11.30 


% 
91.82 
8.18 
1.31 
0.39 
3.07 
1.85 
8.97 


% 


Total nitrogen 


1.30 


Free-reducing substances. 

Sucrose 

Starch 


3.16 
1.60 
8.40 



50 



Table XIX. — Series K. 
All results computed to a green-weight basis. 





Upper leaves 


Lower leaves 


Upper stems 


Lower stems 




First 


Second 


First 


Second 


First 


Second 


First 


Second 




deter. 


deter. 


deter. 


deter. 


deter. 


deter. 


deter. 


deter. 




% 


% 


% 


% 






% 


% 


Moisture 


89.06 




91.26 




93.16 




91.82 




Dry matter 


10.94 




8.74 




6.84 




8.18 




Total nitrogen 


0.441 


0.433 


0.248 


0.224 


0.172 


0.166 


0.107 


0.106 


Nitrate nitrogen 


0.004 


0.004 


0.008 


0.012 


0.012 


0.009 


0.032 




Free-reducing substances. 


0.3.3.5 


0.347 


0.1.54 


0.159 


0.774 


0.773 


0.251 


0.259 


Sucrose 


0.169 




0.080 




0.056 




0.151 


0.131 


Starch 


1.654 


1.585 


0.195 


0.181 


0.370 


6.348 


0.734 


0.687 



Table XX. — Series L. 
All results computed to a dry-weight basis except moisture and dry matter. 



Material 


Upper leaves 


Lower leaves 


Upper stems 


Lower stems 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


Moisture 


% 
86.10 
13.90 
3.35 
0.06 
2.47 
1.73 
18.38 


% 

3.37' 

2^46 
2.06 
18.39 


% 
88.50 
11.50 
2.78 
0.16 
3.00 
1.39 
4.15 


% 

'2^51' 
0.13 
3.00 
1.42 
4.17 


% 
89.90 
10.10 
1.69 
0.06 
9.22 
3.39 
8.53 


% 

1:59' 
0.07 
9.20 
3.53 
8.29 


% 
88.27 
11.73 
.97 
0.52 
5.20 
4.39 
13.64 


% 


Total nitrogen 


1.12 
0.47 


Free-reducing substances. 

Sucrose 

Starch 


5.40 
4.44 
13.40 



Table XXI. — Series L. 
All results computed to a green-weight basis. 



Material 


Upper 

First 
deter. 


leaves 

Second 
deter. 


Lower leaves 


Upper stems 


Lower stems 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


Moisture 


86 .'100 
13.900 
0.464 
0.008 
0.343 
239 
2.553 


% 

'0^468 

0^342 
0.286 
2.555 


% 
88.500 
11.500 
0.319 
0.019 
0.344 
0.159 
0.476 


% 

'6!288 
0.015 
0.344 
0.162 
0.480 


% 
89.900 
10.100 
0.170 
0.006 
0.930 
0.342 
0.861 


% 

0.160 
0.007 
0.929 
0.356 
0.837 


% 
88.270 
11.730 
0.113 
0.061 
0.610 
0.514 
1.600 


% 




0.132 


Nitrate nitrogen 

Free-reducing substances. 

Sucrose 

Starch 


0.055 
0.633 
0.520 
1.572 



Within the steins from top to bottom there is a decreasing gradient in moisture, 
total nitrogen, and free-reducing substances and an increasing gradient in suc- 
rose, polysaccharides, and total dry matter. 

Experiment VII. For this experiment seeds of the variety Lorrillard were 
sown February 2, 1917, and the young plants transplanted to two and one-half- 
inch potsof rich soil February 14, 1917. OnMarchlOtheseplants were from four 
to five inches tall, stocky, and green, but in need of repotting. Some showed 
small flower buds clearly. On this date the plants were transferred to ten- 
inch pots containing rich soil. Further treatments are described in the series 
which follow. 

51 



Series M. The plants in the series were grown from March 10 to March 23 
in ten-inch pots in a soil mixture of clay loam one-fourth, sand one-fourth, well 
rotted manure one-half, and were copiously watered. Two plants were grown 
in each pot. At the time of sampling they were eight to ten inches tall, dark 
green with full heavy foliage, succulent, vigorous, and usually showed a well- 
developed bud cluster, none of the single buds of which showed any yellow of 
the corolla. Generally one of the two plants was taken from each pot though 
in some instances both were removed. (The plants remaining were used in 
series Q and R.) The samples were taken at 2.00 p. m. on a clear day. The 
analyses of these plants are used for comparison with those collected later in 
the other series of this experiment. 



Table XXII.— Series M. 
All results computed to a dry-weight basis except moisture and dry matter. 



Material 


Leaves of whole 

plant 

First sample 


Leaves of whole 

plant 
Second sample 


Stems of whole 

plant 

First sample 


Stems of whole 

plant 
Second sample 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


Moisture 


% 
90.61 
9.39 
4.11 
0.76 
2.08 
1.15 
11.25 


% 

'2;65' 


% 
90.24 
9.76 
3.85 
0.50 
1.30 
1.04 
10.92 


% 
L40 


% 
94.16 
5.84 
2.75 
1.62 
0.80 
0.46 
0.89 


% 


% 
93.94 
6.06 
2.94 
1.63 
1.24 
1.06 
3.08 


% 










Free-reducing substances. 

Sucrose 

Starch 


3^05 



Table XXIII— Series M. 
All results computed to a green-weight basis. 





Leaves of whole 

plant 

First sample 


Leaves of whole 

plant 
Second sample 


stems of whole 

plant 

First sample 


stems of whole 

plant 
Second sample 


Material 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


Moisture 


% 
90.61 
9. 39 
0.385 
0.072 
0.195 
0.108 
1,056 


% 
0^192 


% 
90.24 
9.76 
0.375 
0.046 
0.126 
0.101 
1.066 


% 

o.m 


70 

94.16 
5.84 
0.160 
0.095 
0.046 
0.026 
0.051 


% 
'o!649 


% 
93.94 
6.06 
0.178 
0.098 
0.075 
0.064 
0.185 


% 






Nitrate nitrogen 

Free-reducing substances. 

Sucrose 

Starch 


oiise 



Series O. On March 10, 1916, some of the plants mentioned in series M 
were removed from the pots in which they were growing, the soil particles care- 
fully and thoroughly washed from the roots, and then they were transplanted 
to ten-inch pots containing quartz sand. Two plants were put in each pot. 
On April 11 and April 19 each pot was given 350 c.c. of nutrient solution free 
from nitrogen. After being transplanted, the plants wilted appreciably but 
recovered within two days. While there was some continued axial elongation, 

52 




63 



growth was decidedly checked, the lower leaves became yellow and fell, though 
for the most part the blossom clusters expanded and in some cases set one or 
two fruits. The stems became yellow, very tough and woody, and stood erect 
with no tendency to tip over. Samples were collected for analysis April 16 at 
2:00 p. m. on a partly cloudy day. At this time the plants were about sixteen 
inches high, erect, light green, the lowermost leaves brown and dry, and in 
some cases already fallen; the upper leaves gray green, small, the stems becom- 
ing yellow, woody, even well above the middle, and scarcely at all succulent, 
the second blossom clusters small and not setting to form fruit. 

Table XXIV.— Series O. 
All results computed to a dry-weight basis except moisture and dry matter. 





Upper 


leaves 


Lower 


leaves 


Upper 


stems 


Lower 


stems 


Material 
































First 


Second 


First 


Second 


First 


Second 


First 


Second 




deter. 


deter. 


deter. 


deter. 


deter. 


deter. 


deter. 


deter. 




% 


% 


% 


% 


% 


% 


% 


% 


Moisture 


81.40 




86.00 




86.98 




84.62 




Dry matter 


18.60 




14.00 




13.02 




15.38 




Total nitrogen 


1.70 


1.73 


1.12 


1.20 


0.90 


0.96 


0.80 


0.83 


Nitrate nitrogen 


0.00 


0.00 


0.00 


0.00 


0.00 


0.00 


0.007 


0.002 


Free-reducing substances . 


3.65 


3.72 


4.02 


4.08 


9.20 


9.23 


9.05 


8.96 


Sucrose 


1.05 


0.78 


0.86 


0.80 


4.00 


4.08 


6.31 


5.70 


Starch 


31.76 


31.85 


16.20 


15.90 


17.98 


18.51 


22.96 


22.51 



Series P. On March 10 the plants in this series were taken from the pots in 
which they were growing, the soil carefully washed from the roots, and, they 
were then transplanted to twelve-inch pots containing quartz sand. Each pot 



Table XXV.— Series O. 
All results computed to a green-weight basis. 



Material 


Upper leaves 


Lower leaves 


Upper stems 


Lower 


stems 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


Moisture 


% 
81.40 
18.60 
0.316 
0.000 
0.679 
0.195 
5.909 


% 

0^323 
0.000 
0.692 
0.145 
5.925 


% 
86.00 
14.00 
0.156 
0.000 
0.563 
0.121 
2.269 


% 

' 0.168 
0.000 
0.572 
0.112 
2.226 


% 
86.98 
13.02 
0.117 
0.000 
1.197 
0.521 
2.340 


% 

'6! 125 
0.000 
1.201 
0.531 
2.409 


% 
84.62 
15.38 
0.123 
0.002 
1.392 
0.970 
3.531 


or 
/o 


Total nitrogen 


0,127 
0.0004 


Free-reducing substances . 

Sucrose 

Starch 


1.378 
0.875 
3.461 



received an application of Knop's solution diluted one to seven on each of the 
following dates: March 10, March 17, March 24, April 2, April 19. An abun- 
dance of moisture was supplied at all times. On April 16 the samples were col- 
lected under the same conditions as series O. At this time the plants were 
eighteen to twenty-four inches high, erect, bright green in color, the leaves 
standing out stiffly from the stems except the lowermost, which were also some- 
what yellowed; each plant had set several fruits. 

54 



Table XXVI.— Series P. 

All results computed to a dry-weight basis except moisture and dry matter. 



Material 


Upper 

First 
deter. 


leaves 

Second 
deter. 


Lower leaves 


Upper 


stems 


Lower stems 


First 
deter. 


Second 
deter. 

% 

'2'.27' 
0.09 
2.08 
0.27 

12.36 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


Moisture 


% 
84.02 
15.98 
2.74 
0.02 
2.60 
0.30 
25.38 


2^80' 
0.03 
2.53 

25^58' 


% 
87.72 
12.27 
2.28 
0.12 
2.08 
0.26 
12.65 


% 
90.82 
9.18 
1.75 
0.21 
8.33 
0.85 
8.70 


% 

i^gi' 

0.13 
8.31 
1.06 
8.54 


% 
88.12 
11.88 
1.25 
0.16 
7.78 
3.58 
11.20 


erf 
10 


Total nitrogen 

Nitrate nitrogen 

Free-reducing substances . 

Sucrose 

Starch 


1.07 
0.18 
7.80 
3.45 
11.25 



Table XXVII.— Series P. 

All results computed to a green-weight basis. 



Material 


Upper 

First 
deter. 


leaves 

Second 
deter. 


Lower leaves 


Upper 


stems 


Lower stems 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


Moisture 


% 
84.02 
15.98 
0.438 
0.003 
0.416 
0.048 
4.055 


% 

0^447 
0.004 
0.404 

'4:087 


70 

87.73 
12.27 
0.280 
0.013 
0.255 
0.103 
1.553 


% 

0^278 
0.011 
0.254 

L517 


% 
90.82 
9.18 
0.160 
0.019 
0.764 
0.078 
0.798 


% 

0^175 
0.011 
0.763 
0.098 
0.784 


88.' 12 
11.88 
0.148 
0.018 
0.924 
0.425 
1.331 


% 




127 




021 


Free-reducing substances . 

Sucrose 

Starch 


0.927 
0.410 
1.337 



Series 0> The plants of this series were transferred on March 10 from small 
pots exactly as in series M previously described. In fact, that series simply 
represents an earlier collection from the same group of plants. An abundance 
of moisture was provided at all times. The plants grew very rapidly, the 
leaves became large and green, and the stems of large diameter and very succu- 
lent. Samples were taken at the same time and under the same conditions as 
those in series O. At that time the plants in the present series were eighteen 



Table XXVIII.— Series Q. 

All results computed to a dry-weight basis except moisture and dry matter. 





Upper 

First 
deter. 


leaves 

Second 
deter. 


Lower leaves 


Upper 


stems 


Lower stems 


Material 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


Moisture 


% 
88.48 
11.52 
4.38 
0.32 
1.04 
0.34 
12.65 


% 


■4:43' 
0.25 
1.04 

12^83' 


% 
91 .'02 
8.98 
3. 35 
0.92 
0.68 
0.47 
4.95 


% 

3.51 
0.83 
0.50 
0.30 
5.10 


% 
94.79 
5.21 
3.27 
2.05 
3.25 
0.17 
1.02 


% 


3^08 

3^18' 
0.24 
1.10 


% 
93.36 
6.64 
2.46 
1.54 
1.51 
1.43 
1.43 


% 




2.53 


Nitrate nitrogen 

Free-reducing substances. 

Sucrose 

Starch 


1.56 
1.29 
1.65 



55 



Table XXIX. — Series Q. 
All results computed to a green-weight basis. 





Upper leaves 


Lower leaves 


Upper stems 


Lower stems 


Material 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


Moisture 


% 
88.48 
11.52 
0.505 
0.036 
0.151 
0.039 
1.458 


% 

oiii 

0.029 
0.151 

'l!478 


% 
91.02 
8,98 
0.301 
0.082 
0.060 
0.027 
0.444 


% 

'o!315 
0.065 
0.045 
0.042 
0.458 


% 
94.79 
5.21 
0.170 
0.107 
0.169 
0.008 
0.053 


% 

oiieo 

'o;i65 
0.012 
0.057 


93.36 
6.64 
0.163 
0.102 
0.100 
0.095 
0.095 


% 


Total nitrogen 


0.168 
0.103 


Free-reducing substances. 

Sucrose 

Starch 


0.085 
0.109 



to twenty-two inches tall, very dark green and succulent, the leaves large, soft, 
and with a decided tendency to droop, the stems green, of large diameter, suc- 
culent, and scarcely at all woody to the touch above the lower one-fourth, with 
the result that the plants required stakes to support them. The plants were 
blooming freely but at this time none of the blooms had set, all having fallen 
soon after the fading of the corolla. 

Series R. The plants in this series correspond in every way to those in 
series Q except that each plant when taken for a sample, bore from two to five 

Table XXX.— Series R. 
All results coviputed to a dry-weight basis except moisture and dry matter. 





Upper 


leaves 


Lower 


leaves 


Upper 


stems 


Lower stems 


Material 
















First 


Second 


First 


Second 


First 


Second 


First 


Second 




deter. 


deter. 


deter. 


deter. 


deter. 


deter. 


deter. 


deter. 




% 


% 


% 


% 


% 


% 


/c 


% 


Moisture 


88.53 




90.37 




93.50 




90.55 




Dry matter 


11.47 




9.63 




6.50 




9.45 




Total nitrogen 


4.13 


4.06 


2.90 




2.71 




1.61 


1.53 


Nitrate nitrogen 


0.16 


0.15 


0.17 


0.20 


0.76 




0.36 


0.42 


Free-reducing substances . 


1.31 


1.39 


0.53 


0.51 


5.13 


4.91 


4.13 


4.10 


Sucrose 


0.58 


0.49 


0.12 


0.14 


0.64 


0.86 


1.47 


1.50 


Starch 


17.33 


17.67 


0.00 


0.00 


1.16 


1.19 


0.51 


0.52 



Table XXXI.— Series R. 
All results computed to a green-weight basis. 



Material 


Upper leaves 


Lower leaves 


Upper stems 


Lower stems 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 


Moisture 


% 
88.53 
11.47 
0.473 
0.018 
0.150 
0.066 
1.987 


% 

'o:466 
0.017 
0.160 
0.056 
2.026 


% 
90.37 
9.63 
0.280 
0.016 
0.050 
0.011 
0.00 


% 

0^019 
0.048 
0.013 
0.00 


% 
93.50 
6.50 

0.049 
0.333 
0,041 
0.075 


% 

0^176 

0^319 
0.056 
0.077 


% 
90.55 
9.45 
0.152 
0,034 
0.390 
0.138 
0.047 


% 


Total nitrogen 


0.144 
039 


Free-reducing substances . 

Sucrose 

Starch 


0.387 
0.142 
0.048 



56 



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fruits ranging in size from that of large peas to good-sized walnuts. The object 
in taking this sample was to determine if any differences in analysis could be 
detected between purely vegetative and vegetative-reproductive plants grown 
under identical conditions. 

Series S. The plants in this series were treated exactly like those described 
in series 0. In fact the plants in this lot which are mentioned as having been 
cut back, are the remaining bases of those which constituted series O, up to 
April 23, on which date the plants were carefully knocked from their pots and 
with the least possible disturbance, roots and adhering sand mass were trans- 
ferred to larger pots in which there was a soil mixture of one-fifth sandy clay 
loam and four-fifths well-rotted manure. At this time the plants which had 
not been cut back had changed very little from the condition described for 
April 16, but those which had been cut back to within an inch or two of the sand 
surface, in the majority of cases had developed one or two sprouts from one- 
quarter to one and one-half inches long. These sprouts were gray green, slen- 
der, and woody. Within three days following the transfer to rich soil, the 
stems and tip leaves began to assume a much brighter green color. Growth 
was resumed almost immediately at the tips, the new leaves pushed out vigor- 
ously, and became large, soft, and dark green, the stem developed above the 
tip following the transfer was much larger in diameter than that below it, was 
dark green, succulent, and more densely clothed with glandular hairs. Later 
the old lower stems also became very dark green, showed a decided secondary 
annular growth coupled with a strong tendency to develop adventitious roots. 
The plants bloomed profusely and began to set some fruit though most of the 
blooms fell as soon as the corolla faded. Many of the plants developed axillary 
shoots. In general, plants which had not been cut back, produced much more 
new growth than those which were cut to stubs. All the samples were of 
plants which had not been cut back. The samples were taken for analysis on 
May 12, 1917, at 2:00 p. m. on a clear day. By that date the plants had made 
from four to six inches of terminal growth which was very succulent and green, 
were producing many flower clusters, a few of which had begun to bloom, and 
the whole stem had again become green. The sample was divided into three 
portions, (1) tips made up of the new growth, (2) middles, which included the 
upper halves of the plants as they were before transplanting and (3) bases, the 
lower halves of the same plants. 



Table XXXIV.— Series N. 
All results computed to a dry-weight basis. 



Material 


Leaves of first lot 
7.195 gr. dry weight 


Leaves of second lot 
7.591 gr. dry weight 


First 
deter. 


Second 
deter. 


First 
deter. 


Second 
deter. 




% 
1.14 
0.04 
2.07 
0.00 
5.26 


1.'02 


% 
0.81 
0.22 
3.17 
0.94 
7.78 


% 
0.64 








2.03 
0.00 
5.00 


3.35 






Starch 


7.97 



58 




as 



Series N. This series is made up of the leaves which fell from the plants 
in series O. Sample 1 represents those leaves which fell first and sample 2 a 
later collection. 

The relatively high amounts of nitrate nitrogen present compared with the 
total nitrogen content is worthy of note. 

Series 0. Compared with series Q and R the plants in this series are very 
low in moisture, fairly low in total nitrogen, and very much higher in free-re- 
ducing substances, sucrose, polysaccharides, and total-dry matter. Nitrates 
were absent with the exception of a trace in the lower stems. Within the stems 
from top to bottom there is a decreasing gradient in moisture and an increasing 
gradient in free-reducing substances, sucrose, polysaccharides, and total-dry 
matter. 

Series P. The plants of this series compared with series Q and R are lower 
in moisture, total nitrogen, and nitrate nitrogen and are higher in free-reducing 
substances, sucrose, polysaccharides, and total-dry matter. Within the stems 
from top to bottom there is a decreasing gradient in moisture, total nitrogen 
and free-reducing substances and an increasing gradient in sucrose, polysac- 
charides, and total-dry matter. Within the leaves this relation does not hold. 

Series Q. The plants of this series compared with those of series R, are 
slightly higher in moisture, total nitrogen, and nitrate nitrogen, and lower in 
free-reducing substances, sucrose, and total-dry matter. Within the stems of 
series Q from top to bottom there is a decreasing gradient in moisture, total 
nitrogen, nitrate nitrogen, and free-reducing substances and an increasing 
gradient in sucrose, polysaccharides, and total-dry matter. In series R within 
the stem from top to bottom there is a decreasing gradient in moisture, total 
nitrogen, nitrate nitrogen, and free-reducing substances and an increasing 
gradient in sucrose and total-dry matter. 

Series S. The analyses of the plants in this series show that the middle 
stems and leaves which are comparable to the upper stems and leaves in series 
O have changed very little in percentage of total nitrogen expressed upon the 
green weight. They have increased in moisture and nitrate nitrogen and have 
decreased very much in total-dry matter, free-reducing substances, sucrose, 
and polysaccharides. Comparing the lower leaves and stems of series O with 
those in series S it is evident that there is a slight increase in total nitrogen, 
nitrate nitrogen, and moisture and a decided decrease in free-reducing sub- 
stances, sucrose, and polysaccharides. 



DISCUSSION. 

Several points stand out clearly after a study of the foregoing data. It is 
particularly interesting to note that the interrelation of nitrogenous and carbo- 
hydrate substances in the leaves themselves is very variable in the several 
series and that these relations are frequently quite the reverse of those in the 
stems. This result might be anticipated perhaps from the general knowledge 

61 



of photosynthesis. It will be better in any future studies of the reserves in 
leaves to collect samples after the plants have had a period in the dark as well 
as from plants which have had several hours of exposure to sunshine. 

The tomato stem is interesting in its general anatomical makeup. The 
structure is brought out in the drawings from sections of vegetative and non- 
vegetative stems, taken from the same general location in both types of plants. 
In addition to the usual structures there is present an internal phloem and 
what appears to be an internal xylem. The internal phloem in the average 
stem is nearly equal in amount to the external, and does not differ greatly 
whether such stems are vegetative or non-vegetative, whereas the internal 
xylem cells show decidedly greater thickening in the non-vegetative stems. In 
one of the later experiments for which we did not secure analyses, a number of 
the plants were completely girdled by removing a half inch ring of cortex near 
the base of each. At the time of ringing, these plants were actively growing 
and the first noticeable change was a vigorous development of a callous-like 
tissue at various points within the girdled area. The plants did not seem to 
suffer greatly from this treatment, and after about a week they began to form 
roots above the girdles. Some of these stems were collected for microscopic 
examination and it was found that the internal phloem within the girdled area 
had greatly increased in amount; in some instances being present in from five to 
ten times as great an extent as in the portions which had not been decorticated. 
The diagrams (figure 14) also show that the xylem in proportion to the pith, is 
much greater in the non- vegetative than in the vegetative stems. In fact the 
greater diameter, succulence, and brittleness of the vegetative stems is due to 
the very large size of the pith and pith cells in proportion to the xylem tissue, 
and the tough, woody nature of the non-vegetative stems is due to exactly the 
reverse conditions. 

In connection with the larger size of the leaves and stems of the vegetative 
plants as compared with the reproductive and the non-vegetative non-repro- 
ductive plants, it is worth while to call attention to the work of Gourley (13) 
and of Heinicke (18, 19). Gourley has suggested that larger leaf surface is as- 
sociated with fruit-bud formation. While this is true to a certain degree, yet 
it is a matter of common knowledge that the largest leaves are freciuently borne 
on the most vigorous vegetative plants, so that increased leaf area in itself does 
not necessarily accompany the attainment of the fruiting condition though it 
may be a correlated factor. That this and several other correlations listed by 
Gourley are thoroughly appreciated by him, is indicated by the fact that he 
states that "a good growth is not antagonistic to a good yield but rather they 
go hand in hand." Heinicke has emphasized the importance of the size and 
diameter of conducting tissue and sap densities in connection with increased 
fruit setting. Whether such increase in the percentage of fruit set is due to 
larger size of conducting tissue is really open to question. No doubt there is 
a close correlation between them but each is probably dependent upon some 
other cause back of both of them rather than that the latter follows as a result 
of the former. It is certain that at least some of the conditions of nutrition 
which result in the production of the small spurs are likewise those which make 

63 



for decreased fruit setting and development, and the large spur is rather an ac- 
companiment of increased fruitfulness than its cause. Many similar correla- 
tions between growth and fruit production have been pointed out by various 
workers in connection with pruning problems. In the work of Lewis and Allen 
on nitrate of soda fertilization, the percentage of setting was greatly increased 
the first season the nitrate of soda was applied, not because there was any im- 
mediate appreciable increase in size of the spur, but because of the change in 
the conditions of nutrition from which greater vegetation followed as an essen- 
tial consequence. Theoretically and practically this change in nutrition could 
be so great, that the response is simply vegetative without an increase of fruit 
production. The means which Heinicke employed, such as sawing partially 
through limbs, pruning, etc., in order to limit the amount of sap which any 
given number of spurs could receive, would modify the quality of such sap 
quite as much as its quantity. Both these factors must be taken into consid- 
eration in interpreting the results obtained. In fact, girdling, even such as 
sawing partly through limbs, has been found to increase fruitfulness and fruit 
setting in some instances. It has even been recommended in practice as a 
means of causing over-vigorous trees to become fruitful. These apparently 
conflicting results are not difficult to interpret. If the carbohydrate factor 
relative to the nitrogenous factor were already higher than that which would 
make for maximum fruit setting, then pruning would tend to reduce the carbo- 
hydrates and thereby increase fruitfulness; whereas sawing through, as the 
analyses of Hibino have shown, would tend to increase them still further and 
a decrease in fruitfulness might be expected. If on the contrary the nitro- 
genous factor were relatively too high, then exactly the reverse results from 
the same practices might be expected, since pruning would tend still further to 
decrease carbohydrates, whereas the sawing would tend to increase them. It 
would be interesting to know the differences in composition of the sap corre- 
lated with the differences in its density, and the relation this has to the devel- 
opment of the abscission layer. How to regulate such composition in practice 
is of prime importance. 

From our experiments with tomatoes and from much corroborative evidence 
from general observed conditions throughout a wide variety of plants, it seems 
quite likely that nitrates play a very important part in the development of the 
abscission layer, especially in vegetative plants; whereas relatively higher 
carbohydrate content makes for continued development of the vascular strands 
of the pedicel and the strengthening of their connection with the fruit spur. 
This would be in keeping with the finding of greater thickening of the xylem 
cells in various parts of the plant under the same conditions, and yet, as is well 
known and was clearly evident in our work, a very marked abscission of fruits 
and blossoms occurs also when the carbohydrate content is relatively very 
high. While several possible explanations present themselves, little would be 
gained by theorizing before much more precise information on the actual chem- 
istry of the abscission of fruits is at hand, for many of the factors apparently 
involved in foliar abscission seem to differ widely from those connected with 
the dropping of fruits. 

64 




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It was observed throughout the experiments that as the plants became less 
vegetative, the leaves began to lose their fresh green color, to turn gray green 
and finally yellowish. In spite of this fact, carbohydrate storage in the stems 
continued. In the very vegetative stems, small plastids containing chloro- 
phyll were to be found in the cortical cells and in the pith cells even to the 
center of the largest stems and especially toward the tips. When the available 
nitrogen in the soil was limited, either by drying out the soil or withholding 
nitrogenous fertilizers, the plants began to turn yellow. This was accompan- 
ied by a complete disappearance of the green pigment from the plastids within 
the cortical and pith cells, and apparently the disappearance of many of the 
plastids themselves, especially when deposition of starch grains within the 
cells became rapid. On supplying nitrate to the soil, such plants as were non- 
vegetative first began active growth at the stem tips. This was associated 
with a greening of the smaller, younger leaves and a very rapid disappearance 
of the starch grains from the pith cells of the stem, first near the tip and then 
progressively down the stem to its very base. Plastids again began to appear 
in these cells and later took on a bright green color. These plastids were es- 
pecially abundant in the cells of the newer growth produced after the applica- 
tion of nitrate fertilizer, but also occurred in the cells of the older growth. 

Throughout all of our experiments the plants grown with an abundant sup- 
ply of available nitrogen were distinctly vegetative and non-fruitful. These 
plants as a whole were higher in total and nitrate-nitrogen and lower in free- 
reducing sugars, sucrose, and polysaccharides than were the distinctly non- 
vegetative plants. Within any given plant, especially those which were grown 
most vigorously and rapidly, the nitrate content was generally greater in that 
part of the stem which was the more vegetative. When the plants were not 
excessively vegetative, however, the total nitrogen was higher in the more 
vegetative portions, but the nitrate readings were greater in that portion of 
the plant where the starch content was also higher. It may be remarked that 
there was some disagreement between the quantitive chemical analyses and 
the microchemical analyses for nitrates; by the latter method the greatest 
quantity of nitrates was always indicated in the most actively growing portion 
of any given stem; whereas this relation was found to be variable according to 
the quantitive macrochemical methods. Just how to account for this or what 
the significance of it may be, must be left for future investigations. The gen- 
eral condition of an association of higher total nitrogen and nitrates with in- 
creased vegetation is in most instances valid, especially in the comparison of 
the stems as a whole in the various series. 

There were some wide variations in the amounts of carbohydrate present 
in the different types of plants. The greatest fluctuation was in the amount 
of free-reducing substances. These were generally highest in the stems of the 
less vegetative plants, when considered as a whole, but within the stems them- 
selves they were sometimes more, sometimes less in the more vegetative por- 
tions. Disaccharides and polysaccharides were far less variable in relation 
to any specific vegetative conditions of the stems, either as a whole or in any 
given portion of it, than were the free-reducing substances. Generally an in- 

71 









FigB. 15 and 16.— Diagrammatic cross sections of stems to show relative development of pith 
(dotted), xylem (converging lines), phloem (solid black) and bast (circles) in Series O (S), Series P 
(K) and Series Q (V). The numbers 1 to 4 indicate region of stem from which section was taken in- 
cluding base, lower middle, upper middle, and tip. 





SI 







Fig. 14.— Cross sections of feebly vegetative (Series O) and vegetative (Series Q) stems of tomato, 
The greater development of the xylem tissue in the former is very noticeable. Though not indicated, 
the development of the pith tissue in the latter was very much greater. CO, collenchyma; END, 
endodermis; B, bast; Ex PH, external phloem; CA, cambium; SEC X, secondary xylem; PX, pri- 
mary xylem; IPH, internal phloem; P, pith cells; IX, internal xylem. 







^ 5 





t» 8 M ■] 



Fig 17 —Diagrammatic cross sections of stem of typical plant from Series S. Sections 1 and 2 
are from the base and what was the top of the plant before transferring to rich soil; both show a dis- 
tinct second growth in the secondary xylem. Sections 3 to 6 are taken at points about five centi- 
meterB apart progressively up the stem to within one centimeter of the tip. 



crease in polysaccharides was closely associated with an increase in disacchar- 
ides, and both were almost uniformly greater in the less vegetative plants and 
in the less vegetative portions of any given stem. This association of starch 
content and condition of vegetation is clearly indicated in figure 18. Asso- 
ciated with greater polysaccharide content was a greater thickening of the 
walls of the xylem parenchyma cells, and in stems of equal age a far greater 
proportion of xylem to cortex and especially to pith. This is made clear in 
figure 14 and the diagrams of entire stems in figures 15 to 17. Starch was always 
found in the starch sheath or endodermis, even in the most actively vegetative 
stems, but was not found in any quantity in the pith cells. Frequently in the 
very vegetative plants, there was no starch storage in the bases of the stems. 
When nitrogen was limited, that is in those cases where the plants were less 
vegetative, starch storage was first noticeable in the pith close to the xylem; as 
more and more storage took place, all of the pith cells, the medullary rays and 
the wood parenchyma became filled with starch grains. 

Our experiments indicate that sucrose is not the first sugar formed by syn- 
thesis but that it is present only in those instances where free-reducing sub- 
stances are high and have been permitted to accumulate. The general situa- 
tion seems to be a graded series from free-reducing substances through sucrose 
to polysaccharides. Our observations, therefore, are apparently not in close 
harmony with those of Parkin (35) on the Snowdrop, for he has stated that in 
that plant sucrose is the first sugar of synthesis. 

The great fluctuation in the amount of free-reducing substances present in 
the various types of stems may be due to a variation in the extent of their utili- 
zation as well as their synthesis, dependent upon the presence of other sub- 
stances in conjunction with which still other compounds are built from them. 
If this were the case, it might be expected that the quantities present at any 
given time or location would vary directly with the degree of such utilization. 
At least two alternatives are conceivable, and although neither of them can be 
proved from the work at hand nor from the various opinions as yet expressed by 
various workers, still they may be suggested. In the first place, if the simpler 
carbohydrates do serve as one of the building stones in the synthesis of amino- 
acids and proteins, or if the synthesis of the latter is conditioned by the avail- 
able supply of carbohydrates, as well as a suitable nitrogen supply, it might be 
expected that the carbohydrates would be built over into these compounds 
more or less rapidly according to the amount of such suitable available nitro- 
gen, and the presence of the other necessary conditions, whatever they may be. 
In the second place, if a suitable nitrogen supply were not available so that the 
simple carbohydrates were not utilized in the formation of nitrogen-containing 
compounds but accumulated as such, then there would be a possibility for their 
being built into the more complex forms such as disaccharides, polysacchar- 
ides, and the like. The tomato plant does not contain or store any consider- 
able quantity of fat, hence estimations of it were not made in our experiments. 
Because of the close relationship between carbohydrates and fat synthesis, 
however, it would seem that there was at least a good possibility that similar 
relations may exist in fat-storing plants. 

76 



Our own experiments give indications that the foregoing ideas on the carb ) 
hydrate transformations may be correct, for with an abundance of avaihible 
nitrates in the soil, the plants themselves are relatively high in total nitrogen 
and nitrate nitrogen, and relatively less in carbohydrates; but when there is a 
limitation of the nitrates, the carbohydrates, first the simple and then the more 
complex, accumulate rapidly, provided of course that other conditions for pho- 
tosynthesis are not prevented. When available nitrogen is added to the soil 
in which such nitrogen-low, carbohydrate-high plants are growing, however, 
they very quickly increase in total nitrogen and nitrate-nitrogen content, and 
become actively vegetative. Associated with such a change is a decrease in 
the same complex carbohydrates. Microscopic examinations were made of the 
plants in series O before transferring to a soil abundant in available nitrogen 
and it was found that the cells of the pith, cortex, and medullary rays and even 
those of the xylem parencyma were packed with starch grains. This was true 
for sections taken up to within one centimeter of the tip. Within three days 
following such transfer, the beginning of the disappearance of the starch grains 
from the center pith cells and cortical cells at the tips of the plants was very 
noticeable. Successive examinations as growth progressed showed an active 
terminal elongation which contained no storage starch except in the starch 
sheath, an active development of secondary xylem in the older portion of the 
stem, and a very rapid, progressive, and finally complete disappearance of the 
starch from the pith and xylem parenchyma and also the cortical cells even 
down to the bases of the stems, where it was last to disappear. It may be 
added that some stems which were thus packed with starch were not given ad- 
ditional nitrates. They finally lost all their leaves except two or three at the 
very tip about one or two centimeters long. These stems remained alive for 
over seven months during which time there was a gradual disappearance of the 
starch in some of them until only traces in the medullary rays and pith could 
be demonstrated, while some of the others contained large starch reserves at 
death. Even after this long period a few of these old, yellowed, leafless, ap- 
parently dead stems put out new buds at a few of the nodes when calcium ni- 
trate solution was applied to the sand in which they were growing. Every one 
of the plants which sprouted still contained carbohydrate reserves. 

While on this point, it is worth while to consider the behavior of the plants 
in experiment VII. The results throw some light on the problem of regenera- 
tion. When the plants which constituted series Q were collected, they were 
vigorously vegetative, and the analyses showed that they were very low in the 
more complex carbohydrates but high in total nitrogen. In taking the samples 
the plants were generally cut off about one-half or three-fourths of an inch 
above the surface of the soil. In most cases this left a bare stub of one to three 
nodes, usually without sprouts but in several cases with sprouts from one-quar- 
ter to one and one-half inches long. In every instance in which no sprouts 
were left the stems rotted without any vegetative response whatsoever, where- 
as when sprouts were present they usually grew rapidly. In several cases 
sprouts one-half inch long withered and rotted also. Now the plants in series 
O were collected in exactly the same way, and it will be remembered these were 

77 








Fig. 18. — Diagrammatic tiection.s, base, middle, and tip, from plants of Series O (S) , Series P (Kj , 
and Series Q (V) to show the range and location (in blue) of starch deposits, as indicated by the Iodine 
test, and the comparative development of pith and secondary xylem. All drawn to the same scale. 

78 



non-vegetative, and very higli in the more complex carljohydrates but relatively 
low in total nitrogen and almost without nitrate nitrogen. Not one had a 
sprout at the base, but after cutting back, none of these stubs decayed. In- 
stead, every one without exception produced from one to three new sprouts, 
which grew vigorously for a short time but ceased before more than one-half 
the volume of the top which had been cut away had been attained. Provided 
no additional nitrate was applied to the sand, they again became filled with 
starch. The rapidity with which these shoots began growth was truly aston- 
ishing. What these sprouts did when appreciable ciuantities of nitrates were 
added to the soil is clearly indicated in figures 9, 10, and 12. 

As previously pointed out, the plants in these two lots differed greatly in 
carbohydrate reserves, and in total nitrogen. Two suggestions present them- 
-selves; first, that without carbohydrate reserves or a means for their synthesis 
'regeneration does not result even though large amounts of nitrates are 
available; and second, that with a carbohydrate reserve, even though ni- 
trates are very much restricted, regeneration takes place very rapidly. It 
must be remembered that the sand-culture plants of series O received traces of 
nitrates or other nitrogen containing compounds in the water supply. The 
very slow growth of the plants before cutting back and the early cessation of 
the vegetative extension of the young shoots indicate that a certain amount of 
nitrogen is recjuired merely for maintenance, and that without additional cjuan- 
tities vegetative extension cannot take place. What the result may be when 
the supply of nitrates is increased is well shown in figure 8 and figure 10. 
.The plants shown in the former were grown as series O and later those which 
•were not cut back analyzed as series S. Two plants had been grown in each 
pot of sand and fertilized with nitrate-free Knop's solution. When the samples 
were taken one plant only was collected. Many of these were then transferred, 
without disturbance, to very rich soil. The plants shown in the latter were 
treated the same as series O, but instead of being transferred to rich soil, cal- 
cium nitrate was added to the nutrient solution. The new sprouts had already 
made considerable growth before the nitrate was added. 

The first noticeable feature is, that the plants in the pots which had 
received additional nitrates, when compared with the plants in those 
which had not received them, made much greater growth, especially 
those plants which had not been not cut back; the second, that the difference 
in the growth of the new sprouts is very much less in the plants which 
had been cut back; and the third that the unpruned plants made much more 
growth than the pruned plants in the same pots when available soil nitrogen 
was increased. In the latter the growth is apparently proportional to the car- 
bohydrate reserve in the stems at the time of transplanting. Even though 
there were much greater quantities o*' available nitrates in the nitrate-ferti- 
lized pots than in the unfertilized, when the carbohydrate reserves had been 
greatly limited through cutting back, the growth was not much greater for the 
first few days. When greater cjuantities of carbohydrates were made available 
through synthesis, however, growth was far more rapid in the fertilized pots. 
In other words, this experiment indicates first, that the limitation of the 

79 



nitrates resulted in the suppression of growth and the accumulation of the more 
complex carbohydrates; second, that the limitation of the carbohydrates, even 
with large quantities of available nitrates in the soil, results in a suppression 
of growth; third, that a rapid vegative extension results from an adjustment of 
the carbohydrates and nitrates relative to one another so that both may be 
utilized in the formation and expansion of such structures; and fourth, that 
such a relationship can be secured either by increasing the nitrates without 
decreasing the carbohydrates, or by decreasing the carbohydrates without in- 
creasing the nitrates. While it is apparent that the amounts of these com- 
pounds relative to one another would be the same in both the above cases, the 
total amounts would be greater in the former and less in the latter, a condition 
faithfully reflected in the amount of growth produced. These considerations 
are very important in the problem of pruning and nitrate fertilization, pre- 
viously discussed in this article. 

One more point to be noted was the behavior of the severed stems of the 
7)lants in the foregoing experiment. Pieces of stems one to four inches long, 
without leaves, and possessing both nodes and internodes were examined micro- 
chemically to learn something of the nature of their content. They were then 
placed on filter paper moistened with distilled water and placed under a bell 
jar in the laboratory. These trials were repeated several times, always with 
the same results. (1) Yellowish stems high in carbohydrates and low in total 
nitrogen and nitrates pushed forth many roots, particularly along the inter- 
nodes, to the length of one to four inches. One or two formed tiny yellowish 
sprouts at the nodes. In ten days to two weeks the roots turned dark and be- 
gan to decay. (2) Greenish stems containing starch and fairly high in total 
nitrogen always produced roots along the internodes and sometimes small 
green sprouts at the nodes. The root production was not so profuse as in the 
foregoing. Decay began in about the same length of time. The succulent 
tops of the same plants without starch reserves all decayed without root or 
shoot production. (3) Green, succulent stems, without starch reserves and 
very low in free-reducing substances but high in total nitrogen and nitrate ni- 
trogen, all decayed without root or shoot production. These results are of in- 
terest in connection with the vegetative propagation of many plants, for which 
purpose the practical grower prefers the more "hardened" or mature portions. 
From the general viewpoint expressed in this paper they are also interesting 
in connection with some other experiments on tomatoes which will not be dis- 
cussed here, except to state that a decided reduction in the development of the 
root systems of the plants accompanied a continued removal of leaves from the 
tops. According to microchemical tests, that practice also resulted in a 
marked decrease in the carbohydrates in the stems, and a decided reduction in 
vegetative extension and fruitfulness. 

The accompanying diagrams, figures 19 to 22, show the relation between the 
percentage of total nitrogen and the percentage of total carbohydrates (free-re- 
ducing substances plus sucrose plus polysaccharides) expressed as dextrose. 
It should be borne in mind that the free-reducing substances, sucrose, and poly- 
saccharides are not absolute determinations, but that these terms are used with 

80 




Fig. 19. Diagram to show the comparative quantitative relationships of the total carbo- 
hydrates (connected by broken line) and total nitrogen content x 7 (connected by solid line) 
arranged on the basis of the descending values for carbohydrates, in the upper stems of the 
several series. 



the significance given under the methods of determination in an earUer part of 
this paper. On the base line of the figure at equal distances apart are arranged 
the series of plants and on the vertical lines are arranged the percentages of 
total nitrogen multiplied by seven and of total carbohydrates, expressed on the 
dry weight. On account of the wide differences in composition of different 
parts of any plant grown under a given set of conditions, only similar portions 
are compared. With but few exceptions increased amounts of total nitrogen 
are associated with decreased amounts of total carbohydrates. This condition 
holds fairly uniformly thorughout the plant with the exception of the lower 
leaves. 

This relation between total nitrogen and carbohydrate storage may be due 
to any one or a combination of reasons, some of which are the following: (1) The 
presence of the nitrogenous compounds or nitrates may retard assimilation or 
the formation of the carbohydrates. (2) It may cause increased respiration 
of the carbohydrates . (3) It may aid in the utilization of the carbohydrates for 
the synthesis of organic nitrogenous substances. No definite, exact data on 
any one of these points are available. It is not worth while, therefore, to at- 
tempt conclusions concerning them, though a few suggestions may not be out 

81 




Fig. 20. Same as Fig. 19 except to show the relationships in the lower stems. 

of place. The much greater leaf area developed by vegetative plants would 
seem to indicate the reverse of the first proposal, nor does the presence of in- 
creased amounts of carbohydrates in the non-vegetative plants of necessity in- 
dicate that they are therefore likewise synthesized in greater quantities. Evi- 
dence for or against the second point is not clear, but in keeping with the gen- 
eral findings of increased respiration accompanying more active growth there 
is a probability that more of the carbohydrates would be thus used in the vigor- 
ously vegetative plants. The third possibility has been previously suggested. 
The utilization of the carbohydrates in this manner as well as in the composi- 
tion of portions of the walls of the new cells being formed and the thickening of 
others, probably affords the main reason why they are found as storage sub- 
stances in relatively smaller quantities in the more actively growing stems. 

In general, there is a close correlation between the amount of nitrate nitro- 
gen, total nitrogen, and moisture. Among others, the several factors which 
follow might aid in accounting for this. (1) The nitrates may have a lyo- 
tropic effect in increasing the water-holding capacity of the plant. (2) Car- 
bohydrates and dry matter, substances which have a relatively lower water- 

82 




Fig. 21. Same as Fig. 19 except to show the relationships in the upper leaves. 




Fig. 22. Same as Fig. 19 except to show the relationships in the lower leaves. 

83 



holding capacity, are greater where total nitrogen is less. (3) The nitrates 
may prevent the lignification and thickening of cell walls which have a rela- 
tively low water-holding capacity. (4) They may aid in rapid growth and 
the formation of new cells which have relatively thinner walls and a greater 
percentage of amphoteric substances whose water-holding capacity is relatively 
large. Then, too, the vacuoles are generally more numerous and larger in the 
decidedly vegetative tissues, and these may furnish more opportunity for the 
retention of water. 

In the absence of conclusive evidence which might show that the lyotropic 
action of the nitrates is of significance, no definite conclusions can be drawn. 
The plants which constituted series O were grown in sand and the nitrates of 
the nutrient Knop's solution were eliminated and partly substituted by calcium 
chloride. Even with the presence of the chloride ion, which has a lyotropic 
effect somewhat similar to the nitrate ion, the plants were very low in moisture. 
Of course since no quantitative chlorine determinations were made there is no 
way of comparing the quantities within the plant, and also the presence of the 
calcium ion may overshadow the effect of the chloride ion. Microchemical 
tests indicated an abundance of chloride in all types of plants. The second and 
third points are self explanatory. There were, however, no specific experi- 
ments on the influence of vacuoles on moisture -holding capacity, but the effect 
of protein-like substances in this regard is fairly well established. Micro- 
scopic examinations showed a lesser increase in cellular thickenings in the 
vegetative stems. 

From the investigations of others as well as our own, it has certainly been 
shown that blooming, pollination, or even fertilization do not necessarily as- 
sure actual fertility even in plants actually considered self-fertile, and it would 
appear that at least some cases of self- or even inter-sterility are due, not so 
much to a stable hereditary character as to the condition of the nutrition of the 
plant under investigation. Both heredity and nutrition must be taken into 
consideration in a study of this problem, and while it is possible profoundly to 
modify the expression of any particular plant dependent upon the conditions 
imposed, it may well be argued that such modifications still remain within 
hereditary limits. Just where such limits can be drawn certainly cannot, as 
yet, be determined off-hand, and much more than the average or so-called 
normal conditions must be investigated. 

In general, the observed results and the analyses made in connection with 
the foregoing experiments tend to support our proposed classification of vege- 
tative and reproductive tendencies insofar as they may be based on a relation- 
ship of the carbohydrate and nitrogenous compounds. Throughout the inves- 
tigation, many questions naturally have suggested themselves; a few of them 
have been indicated. We hope that further and more extended investigations 
may be instituted and conducted not only to establish or deny the general 
hypotheses proposed, but to furnish accurate and reliable data on which to 
base interpretations of the more intimate processes and compounds concerned. 



84 



SUMMARY 

1. Plants grown with an abundant supply of available nitrogen and the 
opportunity for carbohydrate synthesis, are vigorously vegetative and un- 
fruitful. Such plants are high in moisture, total nitrogen, nitrate nitrogen, 
and low in total dry matter, free-reducing substances, sucrose, and poly- 
saccharides. 

2. Plants grown with an abundant supply of nitrogen and then transferred 
and grown with a moderate supply of available nitrogen are less vegetative but 
fruitful. As compared with the vegetative plants, they are lower in moisture, 
total nitrogen, and nitrate nitrogen, and higher in total dry matter, free-reduc- 
ing substances, sucrose, and polysaccharides. 

3. Plants grown with an abundant supply of nitrogen and then transferred 
and grown with a very low supply of available nitrogen are very weakly vegeta- 
tive and unfruitful. As compared with the vegetative plants, they are very 
much lower in moisture and total nitrogen and are lacking in nitrate nitrogen; 
they are much higher in total dry matter, free-reducing substances, sucrose, 
and polysaccharides. 

4. When plants which have been grown with a large supply of available 
nitrogen and moisture are subjected to a reduced moisture supply just about 
the wilting point there is a decrease in vegetative activity. These plants com- 
pared with those which are vigorously vegetative, are lower in total nitrogen 
and nitrate nitrogen and higher in free reducing substances, sucrose, and poly- 
saccharides. 

5. Whatever the conditions under which a plant has been grown, consid- 
ering the whole plant as a unit, increased total nitrogen and more particularly 
increased nitrate nitrogen are associated with increased moisture and de- 
creased free-reducing substances, sucrose, polysaccharides, and total dry 
matter. 

6. Fruitfulness is associated neither with highest nitrates nor highest 
carbohydrates but with a condition of balance between them. 

7. There is a correlation between moisture content and nitrate nitrogen. 
This is probably due largely to the preponderance of non-carbohydrate ma- 
terials to carbohydrates in the cases where nitrates are abundant. 

8. In general, within the plant itself, in the stem from the top to bottom, 
there is a descending gradient of total notrogen and moisture, and an ascending 
gradient in total dry matter, polysaccharides and sucrose. The proportion of 
free-reducing substances to other carbohydrates, total nitrogen, and nitrate 
nitrogen is variable. 

9. The great variations in the amount of carbohydrates in plants grown 
under different nutrient conditions and in different parts of the same plant 
indicate that in studying problems concerned with plant metabolism it is neces- 
sary to know the specific environment of the plant as a whole and of its several 
parts. 

10. The conditions for the initiation of floral primordia and even blooming 
are probably different from those accompanying fruit setting. The greatest 
number of flowers are produced neither by conditions favoring highest vegeta- 
tion nor by conditions markedly suppressing vegetation. 

11. Lack of fruit development is not alone due to the lack of pollination or 
fertilization. The flowers may fall soon after pollination (markedly vegeta- 
tive plants) or remain attached for many days without development of the 
fruit (markedly non- vegetative plants). 

85 



12. The tomato stem in cross section is made up of an epidermis from which 
arise glandular hairs, several layers of cortical cells, endodermis, a more or less 
interrupted layer of bast cells, the phloem with small patches of sieve cells, 
primary and secondary xylem, small patches of internal phloem and internal 
xylem separated from each other and the protoxylem of the outer bundles 
by pith cells, and lastly the pith. 

13. Vigorously vegetative stems are much greater in diameter than those 
which are feebly vegetative. This is due to the greater number and size of the 
pith cells in the former and is accompanied by a marked proportional reduction 
in xylem. The collenchyma of the cortex is much less and the walls of the bast 
and internal xylem much thicker in feebly vegetative stems than in those 
which are vigorously vegetative. 

14. Starch is present in the starch sheath of all stems. Starch storage in 
the stems begins first in the pith cells near the primary vascular bundles, then 
extends throughout the pith, xylem, and the cortical cells. 

15. In vegetative stems there is a much greater number of chloroplasts. 
These are present even in the central cells of the pith. In stems very feebly 
vegetativ-^ there are no observable chloroplasts in the pith and their number 
and intensity of coloration is greatly reduced both in the cortex and in the 
leaves. 

16. Stems without storage starch at the base when cut off close to the sur- 
face of the soil, fail to sprout but decay quickly, whereas those with large stor- 
age produce new shoots. Accompanying such growth there is a total or com- 
plete disappearance of the starch, depending upon the relative amount of 
growth made and the available nitrogen supply. If the latter is abundant 
vegetative extension is relatively great; if not, such extension soon ceases and 
starch is again stored in the new growth. 

17. The available corbohydrates or the possibility for their manufacture 
or supply, constitute as much of a limiting factor in growth as the available 
nitrogen and moisture supply. When the opportunity for carbohydrate manu- 
facture within the plant itself is greatly reduced or eliminated even though 
there is a relative abundance of moisture and available nitrogen, vegetation is 
decreased. But when there is a carbohydrate reserve within the tissues under 
the same conditions of nitrogen and moisture supply, growth is active. Very 
large proportional reserves of carbohydrates to n.oisture and nitrate supply, 
also accompany decreased vegetation. 

18. Parts of the stems or cuttings of plants with a large amount of storage 
carbohydrates and particularly those parts where such storage is localized, 
when supplied with moisture or moist conditions, produce roots abundantly. 
This would be of particular interest in vegetative propagation. 

19. Microchemical tests indicate very little difference in potassium con- 
tent of individual cells whatever the condition of the plant. 

20. Withholding moisture from plants grown under conditions of relative 
abundance of available nitrogen results in much the same condition of fruitful- 
ness and carbohydrate storage as the limiting of the supply of available nitro- 
gen itself. 

21. Fertilizers containing available nitrogen or that which may be made 
available, are mainly effective in producing vegetative response. They may 
either increase or decrease fruitfulness, according to the relative available car- 
bohydrate supply. 

22. Irrigation or moisture supply is effective in increasing growth or fruit- 
fulness only when accompanied by an available nitrogen supply and vice versa. 



The effectiveness of the nitrogen value of leguminous cover crops is (lei)en(lent 
upon the accompanying moisture supply. 

23. Cultivation is largely efTective in conserving moisture and in promot- 
ing the supply of available nitrogen. If in any given soil, moisture and avail- 
able nitrogen are already present in quantities such that the plants giovving 
upon it are largely vegetative, a decrease in cultivation will tend towards 
fruitfulness. 

24. Non-leguminous companion crops or cover crops remove from the soil 
both available nitrogen and moisture. In regulating vegetation and fruitful- 
ness by this means the relations of the available moisture, nitrogen, and 
carbohydrates largely determine the result. 

25. Pruning is largely effective in promoting or retarding fruitfulness by 
its effects in balancing the carbohydrate supply within the plant, or the means 
for its manufacture, with the available moisture and nitrogen supply. 

26. Girdling or ringing of the cortex or bark is effective through a modifica- 
tion of the carbohydrate-nitrate relationship. In practice the entire i-ange of 
effects due to such a relationship may be expected from its application. 

27. Fruit production is seemingly a specialized vegetative function usually 
more or less closely associated with the function of gametic reproduction. 
Parts concerned in reproduction range from but little-modified vegetative 
parts to those highly modified portions classified as fruits. The degree in 
which such modification is expressed, is dependent upon physiological changes 
within any specific plant, and may vary widely within the same variety or 
even the same individual. 

28. At least some of the instances of sterility considered to be the result of 
physiological incompatibility may be due to the state or condition of nutrition 
of the plant itself. 

29. Until more exact information is available, both environmental and 
hereditary factors must be considered in any attempted explanation of the re- 
productive or vegetative behavior of plants. 



ACKNOWLEDGMENTS 

The writers are indebted to the authorities of the Oregon Agricultural Col- 
lege Experiment Station for permission to carry on the foregoing studies away 
from the home Station. They desire especially to express their thanks and 
appreciation to Doctor Wilham Crocker of the Department of Botany of the 
University of Chicago, for constant counsel and suggestions during the pro- 
gress of their work, and to Doctor Sophia H. Eckerson of the same Department 
for advice and direction, particularly on the microchemical studies. 



LITERATURE CITED 

1. Alderman, W. H.; Auchter, E. C. 

1916. "The Apple as Affected by Varying Degrees of Dormant and 
Seasonal Pruning." In W. Va. Univ. Agr, Exp. Sta. Bui. 158 
p. 1-56. 

2. Batchelor, L. D.; Goodspeed, W. E. 

1916. "The Summer Pruning of a Young Bearing Apple Orchard." 
In Utah Agr. Col. Exp. Sta. Bui. 140 ]). 1-14. 

87 



3. Bedford, Duke of; Pickering, S. U. 

1911. In Thirteenth Report Woburn Exp. Fruit Farm. 

4. Briggs, L. J.; Jensen, C. A.; McLane, J. W. 

1916. "Mottle-leaf of Citrus Trees in Relation to Soil Conditions." 
In Journ. Agr. Res. v. 6. no. 19 p. 721-740. 

5. Crocker, W. 

1916. "Periodicity in Tropical trees." In Bot. Gaz. v. 62 p. 244-246. 

6. Davis, B.M. 

1915. "A Method of Obtaining Complete Germination of Seed in 
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